Design and Selection Guidelines
for FRP Pultruded Structures
SG.01 (24)
1
DESIGN AND SELECTION
GUIDELINES FOR FRP
PULTRUDED STRUCTURES
Authors
Francisco De Caso, Ph.D., LEED A.P.
University of Miami
Alvaro Ruiz Emparanza, Ph.D.
University of Miami
Ehsan Harati Khalilabad
University of Miami
The following individuals are acknowledged and thanked for their contributions and reviews of this document.
Dustin Troutman, Creative Pultrusions
Jeremy Mostoller, Creative Pultrusions
Bhyrav Mutnuri, Strongwell
Barry Myers, Strongwell
John Busel, ACMA
Kevin Walsh, University of Notre Dame
Eduard Allende Chicota, University of Miami
Mohammed Al Mehthel, Aramco
Gusai Al Aithan, Aramco
William Gold, ACI
Neven Krstulovic-Opara, ExxonMobil
Antonio Nanni, University of Miami
Oscar Daniel Salazar Vidal, Aramco
Aparna Deshmukh, NEx
Jerzy Zemajtis, NEx
2
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
NEx Board of Directors
President
Waleed Al-Otaibi
Chair
Randall Poston
Directors
Ronald Burg
Antonio Nanni
Riyadh Shiban
NEx Steering Committee
Chair
Mohammed Al Mehthel
Members
Gusai Al Aithan
William Gold
Neven Krstulovic-Opara
Antonio Nanni
Oscar Daniel Salazar Vidal
SG.01 (24) Design and Selection Guidelines for FRP Pultruded Structures
ISBN 978-1-963958-00-3
Copyright © 2024 NEx
Copyright by NEx, ACI Center of Excellence for Nonmetallic Building Materials,
Farmington Hills, MI. All rights reserved. This material may not be reproduced
or copied, in whole or part, in any printed, mechanical, electronic, film, or other
distribution and storage media, without the written consent of NEx.
The users of NEx documents occasionally find information or requirements that
may be subject to more than one interpretation or may be incomplete or incorrect. Users who have suggestions for the improvement of NEx documents are
requested to contact NEx via email. Proper use of this document includes periodically checking for errata for the most up-to-date revisions.
NEx documents are intended for the use of individuals who are competent to evaluate the significance and limitations of its content and recommendations and who
will accept responsibility for the application of the material it contains. Individuals
who use this publication in any way assume all risk and accept total responsibility
for the application and use of this information.
All information in this publication is provided “as is” without warranty of any kind,
either express or implied, including but not limited to, the implied warranties of
merchantability, fitness for a particular purpose or non-infringement.
NEx Staff
Executive Director
Jerzy Zemajtis
NEx and its members disclaim liability for damages of any kind, including any
special, indirect, incidental, or consequential damages, including without limitation, lost revenues or lost profits, which may result from the use of this publication.
Technical Director
Aparna Deshmukh
It is the responsibility of the user of this document to establish health and safety
practices appropriate to the specific circumstances involved with its use. NEx does
not make any representations with regard to health and safety issues and the use of
this document. The user must determine the applicability of all regulatory limitations before applying the document and must comply with all applicable laws and
regulations, including but not limited to, United States Occupational Safety and
Health Administration (OSHA) health and safety standards.
Aramco Liaison Director
Gusai Al Aithan
Participation by governmental representatives in the work of NEx and in the development of Center’s documents does not constitute governmental endorsement of
NEx or the documents that it develops.
Order information: NEx documents are available in print or by download and may
be obtained by contacting NEx.
Front cover photo: World's Longest Clear-Span FRP Bridge, Bermuda (photo courtesy Creative Composites Group)
Back cover photo: World's Largest Freestanding FRP Utility Tower, Texas (photo
courtesy Strongwell)
NEx, ACI Center of Excellence for Nonmetallic Building Materials
38800 Country Club Drive
Farmington Hills, MI 48331 USA
info@nonmetallic.org
+1.248.848.3170
EXECUTIVE SUMMARY3
EXECUTIVE SUMMARY
Non-metallic (NM) pultruded composites shapes, herein referred to as Fiber
fiber-reinforced polymer (FRP) composites provide durable and cost-effective
solutions that have been extensively tested and validated as an alternative to traditional building materials (such as wood, steel, aluminum). FRP pultruded systems
are readily available at all built environment scales: from large infrastructure, to
commercial, all the way to residential. FRP pultruded elements are readily available at all built environment scales: from large infrastructure, to commercial and
residential. While FRP pultruded solutions may appear to be new and innovative,
they have been used for several decades.
The pultrusion process of FRP composites allows the manufacturing of limitless
shapes and structural profiles for use in any type of construction. FRP pultruded
composites offer: i) corrosion free structures, ii) high chemical resistance,
iii) lightweight (1/4 that of steel), iv) high tensile strength, v) non-interference
to magnetic fields and radar frequencies. This translates into: i) long life-cycle
service exceeding 100 years of strength retention in corrosive environments, ii)
excellent whole-of-life savings (low, or maintenance free structures), iii) ease of
handling and installation reducing construction and labor costs; and iv) reduced
transportation costs.
Today, FRPs are supported by accepted and recognized material, design and
standards; however, FRP pultruded solutions are typically not commonly known,
and typically limited to niche applications or projects. While adoption of these
systems could be widespread to leverage the extensive range of benefits offered
by FRP pultruded solutions, the lack of familiarity and awareness by engineers,
owners, and specifiers is a persistent barrier. Since no single document in the open
literature provides an overview for the use of FRP pultruded elements, this document provides stakeholders across the building environment the necessary knowledge and tools to understand the “why, what, and how” of FRP pultruded solutions
for the built environment, by:
1.
Presenting the different readily available FRP pultruded solutions and
applications;
2.
Identifying the benefits of FRP pultruded solutions applied in the built
environment, addressing the challenges and opportunities such systems;
3.
Referencing the relevant NM pultruded material qualification and testing
specifications;
4.
Introducing the design guidelines and other relevant documents for using
NM pultruded solutions in built infrastructure projects.
In summary, the economic and performance advantages of FRP pultruded
composites compared to traditional building materials are evident. This document provides readers with a comprehensive and up-to-date overview of properties, design, and use of FRP pultruded components, their connection methods and
resulting structures, with the underlying objective to aid stakeholders in the implementation within building applications and beyond. Ultimately, FRP composites
are an enabling material solution for the building industry.
4
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
ACKNOWLEDGEMENTS
The authors are grateful for support provided by NEx, an ACI Center of Excellence for Nonmetallic Building Materials and its member companies,* the National
Science Foundation (NSF), and the Center for the Integration of Compos­ites into
Infrastructure (CICI) at the University of Miami under the grant #NSF-1916342.
Additionally, the contributions provided by Dustin Troutman and Jeremy Mostoller
from Creative Composites Group; dba Creative Pultrusions, Inc., and Bhyrav
Mutnuri and Barry Myers from Strongwell are acknowledged. The authors would
also like to acknowledge all reviewers for their technical and editorial comments,
as well as their efforts to bring this document to completion.
The opinions expressed in this document are solely those of the authors.
NEx is grateful for funding support from the founding and sustaining member
- Aramco Americas.
NEx member companies:
Sustaining: Aramco
Gold: ExxonMobil
Bronze: MST Bar, Owens Corning, GatorBar, Dextra, Creative Composites
Group, Galen Panamerica, IKK Mateenbar, Comp­King, Strongwell, Rochling
*
Table of Contents5
TABLE OF CONTENTS
EXECUTIVE SUMMARY
3
ACKNOWLEDGEMENTS
4
1. INTRODUCTION
9
2. BACKGROUND
2.1 HISTORICAL OVERVIEW
2.2 BUILT INFRASTRUCTURE APPLICATIONS OVERVIEW
10
10
10
3. FRP PULTRUDED COMPONENTS: HOW
3.1 PULTRUSION PRECURSOR
3.2 FRP PULTRUSION
3.2.1 Reinforcement Materials
3.2.2 Resin Bath
3.2.3 Surfacing Veil
3.2.4 Preforming
3.2.5 Forming and Curing
3.2.6 Pulling System
3.2.7 Cut-off Saw
3.2.8 Finishing Processes
3.3 FIBERS IN FRP
3.3.1 Role of Fibers
3.3.2 Fiber Orientation
3.3.3 Glass Fibers
3.3.4 Carbon Fibers
3.3.5 Basalt Fibers
3.3.6 Aramid Fibers
3.3.7 Other Polymer Fibers
3.4 SIZING IN FRP
3.5 RESIN IN FRP
3.5.1 Role of Resin
3.5.2 Themoset vs. Themoplastic
3.5.3 Epoxy
3.5.4 Polyester and Isophthalic Polyester
3.5.5 Vinyl Ester
3.5.6 Polyurethane
3.5.7 Phenolic
3.5.8 Acrylic
3.5.9 Other Thermoplastics
16
16
16
16
17
18
18
18
19
20
20
21
21
22
23
24
26
27
28
29
30
30
31
32
32
33
33
34
34
35
4. FRP PULTRUDED COMPONENTS: WHERE
4.1 APPLICATIONS & SECTORS OVERVIEW
4.1.1 Non-Civil Infrastructure
4.1.2 Civil Infrastructure
4.2 COMMON COMPONENTS
4.3 GENERAL CONSTRUCTION
4.3.1 Structural Framing
4.3.2 Concrete Reinforcement
4.3.3 Cladding and Fenestration
4.3.4 Pedestrian Bridges and Boardwalks
4.3.5 Vehicular Bridge Decks
4.4 INDUSTRIAL PLANTS
4.5 TRANSPORTATION
4.5.1 FRP for platform structures
4.5.2 Posts and fences
36
36
36
37
38
39
39
41
44
44
46
47
48
48
48
6
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
4.6 WATERFRONT
4.6.1 Fender Systems
4.6.2 Sheet Pile Walls
4.6.3 Dock and Marinas
4.6.4 Offshore Structures
4.7 UTILITY AND TELECOMUNICATIONS
4.7.1 Utility Poles
4.7.2 Cross-Arms
4.7.3 FRP Panels
4.7.4 Industrial Tanks & Processing Equipment
49
49
51
51
52
52
52
52
54
54
5. FRP PULTRUDED COMPONENTS: WHY
5.1 FRP KEY ATTRIBUTES
5.2 GENERAL CONSTRUCTION
5.2.1 Structural Framing
5.2.2 Concrete Reinforcement
5.2.3 Cladding and Fenestration
5.2.4 Pedestrian Bridges and Boardwalks
5.2.5 Vehicular Bridge Decks
5.3 SPECIALIZED CONSTRUCTION
5.3.1 Data Centers
5.3.2 Industrial & Specialized Buildings
5.4 TRANSPORTATION
5.5 WATERFRONT
5.6 UTILITY AND TELECOMUNICATIONS
5.7 FRP vs. TRADITIONAL MATERIALS
5.7.1 Cost
5.7.2 Weight
5.7.3 Tensile Strength
5.7.4 Modulus of Elasticity
5.7.5 Shear Modulus
5.7.6 Thermal Properties
56
56
57
57
57
58
58
58
59
59
59
59
60
60
61
61
62
63
63
64
64
6. FRP TESTING STANDARDS
6.1 CONSTITUENT MATERIAL TESTS
6.1.1 Fiber
6.1.2 Resin
6.2 FRP MATERIAL TESTS
6.2.1 Lamina Level
6.2.2 Laminate Level
6.2.3 FRP Pultruded Components
6.3 FULL-SECTION TESTS FOR FRP PROFILES
6.4 NON-DESTRUCTIVE TESTS
6.4.1 Visual Inspection Testing
6.4.2 Sounding Testing
6.4.3 Ultrasonic Testing
6.4.4 Vibrational (modal) Testing
6.4.5 Infrared Thermographic Testing
6.4.6 Acoustic Emission Testing
6.4.7 Acoustic-Ultrasonic Testing
6.5 QUALITY CONTROL AND QUALITY ASSURANCE
65
65
65
66
67
68
68
68
71
72
73
74
74
74
75
75
76
76
7. FRP PULTRUDED SPECIFICATIONS
7.1 PURPOSE OF SPECIFICATIONS
7.1.1 Performance and Quality
7.1.2 Safety and Reliability
7.1.3 Compatibility and Interchangeability
7.1.4 Design Process
79
79
79
79
79
79
Table of Contents7
7.1.5 Manufacturing and Process Optimization
7.1.6 Regulatory Compliance
7.2 CONTENT OF A STANDARD SPECIFCIATION
7.3 FRP PULTRUDED SPECIFICATIONS
7.3.1 Design Specifications
7.3.2 Material Specifications
7.3.3 FRP Component Specifications
7.3.4 Project / Construction Specifications
7.3.5 Quality Control Specifications
7.4 GAPS IN FRP PULTRUDED SPECIFICATIONS
7.4.1 Application Specifications
7.4.2 Long Term Performance
7.4.3 Fire Performance
7.4.4 Unification of Standards
80
80
80
82
83
83
83
83
84
84
85
85
85
86
8. FRP DESIGN: GUIDELINES & JOINTS
8.1 DESIGN STANDARDS
8.1.1 Codes and FRP Composites
8.1.2 ASCE/SEI 74
8.1.3 CEN/TC prEN 19101
8.1.4 Manufactures’ Design Manual
8.1.5 Other Design Resources
8.2 DESIGN PHILOSOPHY
8.2.1 Allowable Stress Design (ASD)
8.2.2 Load and Resistance Factor Design (LRFD)
8.3 JOINTS & CONNECTIONS
8.3.1 Bolted Joint
8.3.2 Adhesive Joint
8.3.3 Hybrid Connections
8.3.4 Interlocking Connections
8.3.5 Failure Modes: Bolted Joints
8.3.6 FRP vs Metallic Bolted Connections
8.3.7 Failure Modes: Adhesive Joints
87
87
87
88
89
91
91
92
92
93
96
96
97
98
99
99
102
102
9. CONCLUDING REMARKS AND FUTURE WORK
9.1 CONCLUSIONS
9.2 FUTURE WORK
105
105
106
10. REFERENCES
107
11. FRP COMPOSITE MANUFACTURERS
110
ANNEX A: TERMINOLOGY USED WITH NM FRP PULTRUDED
COMPONENTS
111
ANNEX B: PROPERTIES OF COMMERCIALLY AVAILABLE NM FRP
PULTRUDED COMPONENTS
123
Pultex® Equal Leg Angles
124
Extren® Equal Leg Angles
125
Pultex® Square Tubes
126
EXTREN® Square Tubes
127
Pultex® Round Tubes
128
EXTREN® Round Tubes
129
Pultex® Wide Flange Sections
130
Pultex® I-Sections
130
Extren® I-Shapes
131
Pultex® Rectangular Tubes
132
EXTREN® Rectangular Shapes
133
8
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Pultex® Unequal Leg Angles
Unequal Leg Angle
Pultex® Channels
Extren® Channels
Pultex® Solid Round Rods
Round Rod
Pultex® Solid Bars
Square Bars
Pultex® Sludge Flights
Structural Tees
Double EXTREN® Channels
Double Angles: EXTREN® Equal Leg Angles
EXTREN® Construction Grade Plate
Flat Strips
F Section
Struts
Kick Plates
Square Tube / Round Hole
Z Section
Slide Guide
Flight channel
Curb Angles
SAFRAIL™ Post or Rail Section
SAFRAIL™ Round Handrail Post or Rail Section
Half Round Rail Section
134
135
135
136
137
137
138
138
139
139
140
141
141
142
142
143
143
144
144
144
145
145
146
146
146
ANNEX C: LIST OF PROJECT EXAMPLES
12.1 GENERAL CONSTRUCTION
12.1.1 Structural Framing
12.1.2 Concrete Reinforcement
12.1.3 Cladding and Fenestration
12.1.4 Pedestrian Bridges and Boardwalks
12.1.5 Vehicular Bridge Decks
12.2 INDUSTRIAL PLANTS
12.3 TRANSPORTATION
12.3.1 FRP for platform structures
12.3.2 Posts and fences
12.4 WATERFRONT
12.4.1 Fender Systems
12.4.2 Sheet Pile Walls
12.4.3 Dock and Marinas
12.4.4 Offshore Structures
12.5 UTILITY AND TELECOMUNICATIONS
12.5.1 Utility Poles
12.5.2 Cross-Arms
12.5.3 FRP Panels
12.5.4 Industrial Tanks & Processing Equipment
147
147
147
147
147
147
147
147
148
148
148
148
148
148
148
148
148
148
148
148
148
ANNEX D: NM FRP PULTRUDED STANDARDS LIST
14.1 Standards and Specifications (per Standard Organization and Type)
American Society of Testing and Materials (ASTM) Test Methods
CEN 13706 Test Methods for FRP Pultruded Profiles
CSA S806 Standard Test Methods for FRP Bars and Laminates
JSCE (Japan Society of Civil Engineers)
14.2 Design Standards
149
149
149
153
153
154
155
1. INTRODUCTION9
1. INTRODUCTION
This document is a comprehensive report on the topic of design and selection
guidelines for fiber reinforced polymer (FRP) pultruded structures. This document
will cover the following topics:
• Define different FRP pultruded components and applications;
• Provide a step by step demonstration of how and where to use pultruded
components;
• Outline common applications and benefits;
• Provide information on material specifications;
• Provide guidelines for product qualification and testing; and
• Provide information on design guideline in jointing methods.
This is a holistic document, proving the information to integrate and deploy
readily available FRP pultruded engineered solutions across different segments of
the construction market, beyond that of buildings. The document provides up-todate references, focusing primarily on the last decade of advancements of work
related to FRP pultruded solutions.
In summary, this document provides a comprehensive description in a clear,
exhaustive, and yet succinct way that offers an overview on the topic of FRP
pultruded composites from key attributes, manufacturing, design, and selection
guidelines as well as established applications of NM pultruded structures. Lastly,
this document includes information on technical and design specifications adopted
in the US as well as Europe on FRP pultruded materials, to aid stakeholders in the
implementation within building applications and beyond.
10
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
2. BACKGROUND
2.1 HISTORICAL OVERVIEW
The pultrusion process for producing fiber reinforced polymer (FRP) profiles
was developed first in the 1950s. Researchers and inventors, including W. Brandt
Goldsworthy, M. K. Howarth, and Robert F. Morrison, were pioneers in developing the pultrusion technique. In 1952, W. Brandt Goldsworthy received a patent
for the pultrusion process, marking an important milestone in the commercialization of pultrusion technology. It was developed as an economical approach for
producing profile shapes with a constant cross-section.
Initially, this technique was primarily used for industrial applications to create
small profiles, where in the 1960s, pultruded elements began to find applications
in the aerospace and defense industries. The lightweight and high-strength characteristics of pultruded composites made them suitable for aircraft components,
such as radomes and antenna support. Throughout the 1970s and 1980s, pultrusion
gained popularity in other various industrial applications. The Structural Plastics
Research Council (SPRC) was established in 1971 by the American Society of
Civil Engineers (ASCE) and a manual was proposed and developed for the design
of structural plastics [1]. The Structural Plastics Design Manual (SPDM) was originally published in 1979 as an FHWA report and subsequently by the ASCE in
1984 [2]. This initial guide was not restricted to pultruded profiles.
Over time, advancements in composite materials, particularly glass FRP, played
a significant role in the growth of pultrusion process. Further development of
new polymeric based resin systems, reinforcements, and additives improved the
mechanical properties and durability of pultruded elements. During the following
decades industries such as construction, automotive, marine, and infrastructure
began adopting pultruded elements for their unique properties, including corrosion
resistance, high strength, and design flexibility.
As the pultrusion industry grew, standardization organizations and trade associations representing the composites industry such as American Society of Civil
Engineers (ASCE), and the American Composites Manufacturers Association
(ACMA), respectively, developed design guidelines and standards focusing on
pultruded elements. These guidelines, which will be discussed in further detail in
this document, provide engineers with design methodologies, material specifications, and performance criteria for various applications of FRP pultruded elements.
In recent decades, pultrusion technology has continued to advance. The process,
which will be presented in detail in this document has become more automated and
efficient, allowing for higher production volumes and more complex shapes. There
have also been advancements in composite materials, including the use of carbon
fibers and hybrid reinforcements in pultrusion.
The industry has grown significantly which has led to the manufacturing of large
FRP profiles that can be used as beams and columns in buildings, bridges and wind
turbines, among other applications. Today, pultruded elements are widely used
in a range of industries, including civil engineering, construction, infrastructure,
transportation, and renewable energy, as it will be reviewed. Ongoing research and
development in pultrusion techniques and materials continue to expand the capabilities and applications of pultruded elements.
2.2 BUILT INFRASTRUCTURE APPLICATIONS OVERVIEW
One of the earliest applications of nonmetallic pultruded elements, was in the
aerospace industry. In the 1960s, pultruded glass FRP composites found use in
aerospace applications due to their lightweight and high-strength properties. One
notable early example is the use of pultruded composite rods for radome supports
on aircraft. The adoption of pultruded FRP composite rods in aerospace applications demonstrated the benefits of FRP pultruded elements, particularly in terms of
weight reduction, corrosion resistance, and structural performance. This success in
2. BACKGROUND 11
the aerospace industry paved the way for the application of pultrusion in various
other sectors, including construction, infrastructure, automotive, and marine.
The first application of FRP pultruded profiles for building large structures
involved single-story gable frames, that were utilized for electromagnetic interference (EMI) test laboratories in the burgeoning computer and electronics industry.
The FRP profiles’ electromagnetic transparency was a significant advantage in
these structures as no magnetic material was necessary above the foundation level.
Custom pultruded profiles and building systems were developed and commercialized by Composites Technology, Inc. (CTI), founded by Andrew Green in Texas in
the 1960s [3]. In 1985, CTI designed and constructed an innovative EMI building
for Apple Inc. During the 1980s, Morrison Molded Fiberglass Company (MMFG,
now Strongwell) in Virginia produced FRP pultruded profiles for constructing
structures like those created by Composites Technology, Inc. These structures were
built for IBM and other companies. Figure 1 shows an FRP gable frame building
during the installation of the FRP cladding. For much of this time, designing was
done by an MMFG subsidiary called Glass-Steel. A design manual for the MMFG
profile shape Extren was published in 1973. Creative Pultrusions (now Creative
Composites Group) began producing standard shapes in the late 1970s, called
Pultex, and developed a design manual. Current editions of these manuals are
published regularly and are available from these two companies.
The cooling tower industry represented a significant milestone in developing
building systems for FRP profiles, which remains to date a significant market
segment for large, pultruded building components. Composite Technology, Inc.
developed an FRP building system for Ceramic Cooling Tower (CCT) in the 1980s
and marketed it as the Unilite system [4]. The Unilite system comprised various
beam, column, and panel FRP pultruded components that were distinct from
conventional building components.
Nowadays, numerous pultrusion
firms manufacture specialized parts
for FRP cooling tower systems which
are supplied to various cooling tower
manufacturers, as shown in Figure 2.
In addition to custom cooling tower
structures, FRP profiles have been used
in ‘‘stick-built’’ cooling towers since
the late 1980s. These systems are typically constructed using tubular FRP
sections 2 X 2 in. (50 X 50 mm) and 3
X 3 in. (75 X 75 mm) covered with an
FRP or nonreinforced polymer cladding
system. Designers typically use standard
off-the-shelf pultruded profiles in these
Figure 1 - FRP gable frame structure under construction (Source: Strongwell)
structures and design them according to
applicable building codes. A stick-built
cooling tower under construction is
shown in Figure 3.
Currently, standard FRP profile
shapes have not been widely adopted
for constructing multistory frame
buildings for commercial or residential purposes. A significant challenge
with multistory frame structures
employing FRP profiles is the development of cost-effective and efficient
methods for connecting individual
members (design and connection
of FRP pultruded elements will be
disused in detail in this document).
Figure 2 - FRP cooling tower (Source: SPX Cooling Technologies, Inc.)
12
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Figure 3 - Stick-built cooling tower under construction (Source: Strongwell).
Since the early 1990s, studies have investigated FRP connections but no straightforward and efficient connection system has been developed or marketed for FRP
pultruded profiles. Most current designs use steel-like connection details that are
not optimized for FRP profiles. Figure 4 illustrates the Eyecatcher, a prototype
multistory framed building built by Fiber line Composites in Basel, Switzerland in
1999. This building was constructed for the Swissbau Fair to showcase the potential of FRP profile shapes [5].
Since the mid-1970s, the use of FRP profile shapes in bridge engineering has
become more prevalent. Small FRP profiles have been used in the construction of
thousands of truss-style short span pedestrian footbridges ranging from 30 to 90
ft (9 to 27 m) in length worldwide. The FRP components’ lightweight nature and
their corrosion resistance make them appealing for use as bridge decking panels
and superstructure members. Figure 5 depicts an FRP bridge constructed by ET
Techtonics.
Maunsell Structural Plastics developed the Advanced Composite Construction
System (ACCS), a FRP plank system used to construct a 131-meter-long cablestayed pedestrian bridge in Aberfeldy, Scotland, in 1992, as seen in Figure 6. The
bridge also utilized a fiber rope called Parafil for the cable stays. Another example
of FRP profile usage in bridge construction is Scandinavia’s first composite
bridge - the Fiberline Bridge – a 40.3-meter-long cable-stayed pedestrian bridge
constructed over a railway line using FRP profiles in Kolding, Denmark, in 1997
as seen in Figure 7. These structures are noteworthy for their extensive use of FRP
pultruded profiles, allowing for quick and cost-effective construction. The design,
development, and construction of FRP pedestrian bridges increased during the 90s
and early 2000s, where for example a 127 m long FRP footbridge was built in 2012
in Floriadebrug, Netherlands while the first pedestrian bridge with a 25 m span
length in Italy was built in 2011 in Prato.
During the 1990s, several FRP manufacturers tried to create an FRP bridge deck
system that could be used with conventional steel or concrete girders. Several
companies, including Creative Pultrusions, Martin Marietta Composites, Atlantic
2. BACKGROUND 13
Figure 4 - Eyecatcher building (Source: Thomas Keller.)
Figure 5 - Light-truss pedestrian bridge pultruded structure (Source: ET Techtonics.)
Research Corp., and Hardcore Composites, have developed and marketed FRP
deck systems [6]. In addition to the potential for long-term durability of an FRP
bridge deck, there is an added advantage when FRP decks are used to replace deteriorated reinforced concrete decks. By decreasing the structure’s dead weight, the
re-decked structure’s live-load capacity can be increased which can be particularly
useful on bridges with load postings.
Despite the potential benefits of FRP decks, such as long-term durability and
increased load capacity, their relative high cost compared to conventional concrete
decks, traditionally limited its use. Additionally, Just like with FRP frame systems,
the connections between prefabricated FRP deck panels and the superstructure and
14
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Figure 6 – FRP and parafil cable-stayed pedestrian bridge in Aberfeldy, Scotland using ACCS
Figure 7 – The Fiberline Bridge in Kolding, Denmark
2. BACKGROUND 15
those between the FRP deck and the superstructure have posed challenges to the
development of the full implementation for this technology. Similarly, developing
an approved bridge guardrail for FRP deck systems has proven difficult and has not
yet been resolved satisfactorily.
In 2001, a glass–carbon FRP pultruded profile 36 in. high by 18 in. wide,
known as the double-web beam (DWB) was developed by Strongwell for use as a
bridge girder. Figure 8 shows FRP girders on the Dickey Creek bridge in Virginia,
constructed in 2001. More recent applications will be discussed in detail in this
document, identifying the state of the practice of FRP pultruded elements used in
the built infrastructure [7].
Figure 8 - FRP DWB girders on Dickey Creek bridge (Source: Strongwell)
16
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
3. FRP PULTRUDED COMPONENTS: HOW
3.1 PULTRUSION PRECURSOR
The pultrusion process was developed due to critical inventions and material
developments including most notably ‘bakelite’ and ‘fiberglas.’ Bakelite remains
historically significant as one of the first synthetic plastics and an important milestone in the development of modern materials. It was a type of synthetic resin
that was the first commercially successful thermosetting resin. It was invented by
Belgian-American chemist Leo Baekeland in 1907 and named after himself. Bakelite is derived from a combination of phenol and formaldehyde which undergo a
chemical reaction known as polymerization. This reaction creates a three-dimensional network of cross-linked polymers, resulting in a hard and rigid material with
excellent electrical insulation properties. Bakelite is often referred to as a “phenolic
resin” due to its composition. Bakelite revolutionized the plastics industry and has
played a significant role in the pultrusion industry.
In 1935, Owens-Illinois, a glass container manufacturer, and Corning Glass
Works, a specialty glass producer, joined forces to establish Owens-Corning
Fiberglas Corporation. The collaboration aimed to explore and commercialize the
potential of fiberglass as a new material. Later in 1938, Owens-Corning Fiberglas
Corporation introduced the first commercially viable fiberglass insulation patenting
‘fiberglas’. This development revolutionized the insulation industry by providing
a lightweight, efficient, and fire-resistant alternative to traditional insulating materials. The use of continuous glass fiber played a significant role in advancing the
use of fiberglass composites in industries such as automotive and construction,
as Owens Corning promoted the use of what was first referred to as fiberglassreinforced plastic, now known as fiber reinforced polymer (FRP) composites in
construction for multiple applications.
Based on the development of this and other resin and fiber products, the concept
of pultrusion began to emerge in the mid-1940s to early 1950s. By the late 1960s
and early 1970s, several pultrusion companies were producing I-shaped and tubular
profiles [8].
3.2 FRP PULTRUSION
FRP refers to a polymer that has been reinforced with continuous fibers such
as glass, basalt, carbon, aramid, or other continuous fibers. When these fibers are
combined with resins, the composite takes on new characteristics that improve its
overall functionality and quality. These characteristics include strength, stiffness,
corrosion resistance, reduced thermal conductivity, electrical insulation and more.
The pultrusion process is a manufacturing method used to produce continuous
lengths of composite materials with consistent cross-sectional profiles. Today, it
is a highly automated and efficient process that involves pulling reinforcing fibers
through a resin bath, forming them into the desired shape, and then curing the
composite material to create a solid, rigid profile. A general overview of the pultrusion process and each of the key aspects of this process is described in Figure
9. Understating the pultrusion process used to manufacture nonmetallic pultruded
elements is a critical aspect for engineers, designers, owners, and other key stakeholders in increasing their assurance and validate the technology in the construction industry [9]. A terminology list containing an array of nomenclature and terms
used within the FRP pultrusion and composites industry is provided in Annex A.
This annex is an aid aimed at improving the learning process for all stakeholders to
become familiar with such terms.
3.2.1 Reinforcement Materials
The pultrusion process typically starts with the selection of reinforcement materials. Today, one of the most used reinforcement fiber types is fiberglass in the form
of rovings with continuous tows (bundle of fibers) or continuous strand mats. Other
reinforcement materials, such as basalt, carbon or aramid fibers are used depending
3. FRP PULTRUDED COMPONENTS: HOW 17
Figure 9 - Pultrusion process. (Source: Pultron Composites)
on the desired properties of the final product. In the next section additional information is provided on the fiber reinforcement materials.
Reinforcement of materials also involves feeding and positioning the fiber
rovings or mats in a controlled manner to ensure proper impregnation with resin
and formation of the pultruded composite product. To this end, the rovings, mats,
or fabrics are typically supplied from spools or creels that hold the continuous fiber
reinforcements and are positioned strategically in the pultrusion line to ensure a
continuous supply of fibers throughout the process. The reinforcement materials
are guided and directed towards the resin bath, where they will be impregnated
with the resin. Guides, tensioning devices, and eyelets are typically used to control
the path and tension of the fibers, ensuring smooth and uniform delivery of the
reinforcement materials.
3.2.2 Resin Bath
The resin bath is where the fiber reinforcement materials are immersed and
impregnated with the resin. The resin bath plays a critical role in saturating the
fibers and ensuring uniform resin distribution throughout. Proper resin bath design,
temperature control, filtration, and maintenance are essential to achieve uniform
resin impregnation and produce high-quality FRP pultruded composite products.
The resin bath essentially contains a pool of liquid resin, which is typically a
thermoplastic or thermosetting polymer. Additionally, at this stage, other distinct
constituents (additives), such as promoters, fire retardants, and colorants, may be
added in small quantities relative to the resin. The fiber reinforcement materials,
such as rovings, mats, or fabrics are pulled through the resin bath, allowing the
fibers to become saturated with the resin. The resin impregnation process aims to
have each individual fiber coated with the resin, creating a strong bond between
the fibers and the resin matrix. To this end, mechanisms to control the resin flow
and impregnation may be incorporated in the process. This may include adjustable guides, rollers, brushes, or injectors that regulate the resin content and facilitate uniform impregnation. The control of resin flow and reinforcement placement
is crucial to achieve consistent resin-to-fiber ratio and avoid resin-rich or resinpoor areas within the final pultruded element. Due to the chemical reaction that
occurs with thermoplastic or thermosetting polymers, where heat is released, the
resin bath may often be heated to a specific temperature to maintain the resin in a
low-viscosity state thus enabling better flow and impregnation of the fibers. The
resin temperature is controlled based on the resin’s curing requirements and the
desired processing conditions. Lastly, filtration systems to remove any impurities
or contaminants from the resin may be utilized in this stage, ensuring a clean and
18
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
high-quality impregnation process. Regular maintenance and cleaning of the resin
bath are essential to prevent resin buildup, maintain consistent resin properties,
and ensure proper resin impregnation over extended production runs.
Some pultrusion line setups employ a resin circulation system within the resin
bath. This system recirculates the resin to maintain consistent resin properties and
temperature throughout the pultrusion process. Resin circulation helps prevent
resin settling, promotes even resin distribution, and reduces the risk of resin
degradation or gelation within the bath. It is important to point out that the resin
type used in the pultrusion process will need to be compatible with the reinforcement fiber sizing. Fiber sizing, also known as fiber sizing agent or fiber finish, is
the coating applied to the surface of individual fibers and serves as an interface
between the fiber and the resin. The sizing improves the compatibility and adhesion between the fiber and resin. Thus, fiber sizing plays a crucial role in enhancing
the overall performance and properties of FRP composite materials. The functions
of fiber sizing are discussed in the next section of this Chapter.
3.2.3 Surfacing Veil
Also known as a surface mat or surfacing veil, is typically a non-woven fabric
or coating layer applied to the surface of the pultruded profile during the manufacturing process. It serves as an additional protective and/or aesthetic layer to the
final FRP composite. The specific choice of surface veil depends on the application requirements, desired performance characteristics, and environmental conditions in which the pultruded profile will be used. They are designed to be compatible with the resin system used in the pultrusion process and are often applied in
combination with other reinforcement materials and is sued for surface protection,
improved surface finish, reduce the fiber exposure and increase corrosion/durability resistance. The surface veil also protects the outer layer of reinforcement
from “fiber blooming” caused by long term exposure to sunlight.
Other FRP pultrusion manufacturing processes such as alternative surface
finishes may be incorporated and can also take place at later stages of the pultrusion manufacturing process. For example, in FRP bars used for concrete reinforcement, sand coating and/or a helically winded strand may be incorporated
immediately after the curing process. This reflects the versatility of the pultrusion
manufacturing process, which can be adapted to suit the FRP composite element
and its intended application.
3.2.4 Preforming
After the resin impregnation a pre-forming stage may be implemented in the
pultrusion process prior to forming and curing, where the resin-soaked reinforcement fiber material is passed through preforming guides or preforming dies.
Preforming can be used in the saturated fibers as a preparation process. It involves
arranging and aligning the fibers in a specific pattern or configuration to optimize
the mechanical properties and performance of the pultruded composite element.
These guides or dies shape the reinforcement into the desired cross-sectional
profile. Additionally, the preforming will help remove excess resin.
It is worth noting that not all pultrusion processes require preforming. In some
cases, continuous fiber reinforcements (typically rovings or tows), are directly
fed into the pultrusion machine without specific preforming steps. The need for
preforming depends on the complexity of the part, the desired fiber orientation,
and the specific requirements of the FRP pultruded product.
3.2.5 Forming and Curing
Forming and curing are two crucial stages in the pultrusion process (that
may happen simultaneously depending on the manufacturing process), where
the saturated reinforcing fibers are pulled through the pultrusion die and pass
through a heated die or oven. Forming and curing in pultrusion are tightly integrated processes that enable the transformation of resin-impregnated fibers into a
final, solid FRP composite. The precise control of the temperature, pressure, and
3. FRP PULTRUDED COMPONENTS: HOW 19
processing parameters during these stages is essential for achieving desired material properties, dimensional accuracy, and overall FRP product performance. The
two stages are described below.
In the forming stage, preheating of the pultrusion die is typically implemented.
The die is typically made of steel and is designed to provide the desired shape
and dimensions to the final FRP pultruded composite product. As part of this
process, the resin-soaked fibers may be pulled through guides or rollers to align
them in the desired orientation. Lastly, the impregnated and aligned fibers enter the
heated die element where they are compacted and shaped into the desired crosssectional profile. This is typically achieved through the use of pulling mechanisms
(as described next), pressure plates, or other forming techniques. Inside the die,
controlled heat is applied to the soon-to-become FRP composite material, causing
the resin to cure and solidify. The high temperature of the die helps facilitate resin
flow, consolidation, and curing.
In the curing stage, as the FRP composite is formed inside the die, heat and
pressure are applied to initiate and promote the curing process of the resin. The
temperature and pressure settings (depending on the manufacturing process set
up), must be carefully controlled and monitored based on the resin system’s curing
requirements. The applied heat and pressure will trigger the chemical reactions
in the resin, causing it to polymerize and cross-link. This results in the resin transitioning from a liquid to a solid state, bonding the reinforcement fibers together
while creating a rigid and durable composite material. The curing process may
also involve exothermic reactions, where heat is generated as a byproduct, further
aiding the curing process. Once the resin has sufficiently cured and hardened (via
cooling means as discussed next), the pultruded FRP element is continuously
pulled through the die. This ensures the profile maintains its shape and dimensions
as it exits the pultrusion machine. After extraction, the pultruded element may go
through a cooling phase to solidify the resin further.
3.2.6 Pulling System
A pulling system is used to continuously draw the pultruded FRP element through
the different stages of the pultrusion machine as it is being formed and cured. The
pulling system plays a critical role in maintaining the desired speed (rate) and
tension (‘pull’ force, thus where the manufacturing process gets its name from) to
ensure proper processing and production of FRP composites being manufactured.
Typically, the pulling system is controlled by a computerized control system that
regulates the pulling speed, tension, and other process parameters.
The key components and functions of the pulling system in pultrusion include
the grippers or caterpillar pullers, which are used to grasp and grip the pultruded
profile as it exits the pultrusion die following the forming and curing process. They
consist of sets of driven belts or clamps that engage with the profile and provide
the necessary pulling force to advance it through the machine. The grippers ensure
continuous movement of the profile and prevent slippage or distortion during
the process. The pulling system also incorporates tension control mechanisms
to maintain consistent tension on the pultruded profile. Tension is controlled by
adjusting the speed of the grippers to match the desired rate of production. Proper
tension control helps ensure uniformity and dimensional stability of the pultruded
profiles. The pulling system also needs to allow for precise speed control to allow
a constant and controlled pulling speed to be maintained. The pulling speed affects
the several previous stages and can affect the resin flow, curing time, and overall
processing conditions so this parameter must be carefully regulated to achieve the
desired product properties and quality.
In some pultrusion processes, depending on the setup, a cooling component may
be integrated into the pulling system or added before or after. These components of
the pultrusion process cool down the pultruded profile after it exits the die to help
solidify the resin and maintain the shape and dimensions of the profile. Cooling
may involve the use of water baths, air cooling systems, or other methods.
20
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
3.2.7 Cut-off Saw
This is typically a machine or tool used to cut the continuous pultruded profiles
into desired lengths as they exit the pultrusion machine. The cut-off saw plays a
crucial role in the final stage of the pultrusion process, ensuring that the profiles
are accurately cut to the required dimensions. Once the FRP composite element
has fully cured, it is cut into the desired lengths. The cut-off saw typically operates
synchronously with the pulling system, ensuring precise length control while not
interrupting the manufacturing process. This step of the process also ensures that
the pultruded elements meet the desired specifications and can be further processed,
assembled, or packaged according to the application requirements.
The cut-off saw is typically equipped with a cutting mechanism, which can be
a rotating blade, a reciprocating blade, or other cutting tools suitable for cutting
FRP composite materials. The cutting mechanism is designed to deliver precise
and clean cuts through the pultruded profiles and includes a length measurement
system to determine the desired length of each cut, hence lengths can be customized. This can be achieved through various methods, such as an encoder, laser
sensor, or manual input. In several pultrusion processes, the cut-off saw is operated
and controlled by a computerized control system that is integrated with the pultrusion machine’s control system, allowing for synchronized operation and communication between the pultrusion process and the cut-off saw. Thus, the full process is
automated to enhance productivity and efficiency. Automated systems can receive
signals from the length measurement system and the pultrusion process control
system to initiate the cutting operation at the correct position and time. This minimizes manual intervention and reduces the risk of errors. Lastly, cut-off saws are
typically equipped with safety features to protect operators and ensure safe operation which includes physical measures such as guards, emergency stop buttons,
safety interlocks, as well as sensors to detect any anomalies or obstructions during
the cutting process.
3.2.8 Finishing Processes
After cutting, the pultruded profiles may undergo additional post-processing
steps carried out on the pultruded elements to achieve desired surface characteristics, dimensional accuracy, aesthetic appearance, and/or functional requirements.
Finishing operations may vary between pultrusion manufacturing processes and
are ultimately designed to help optimize the performance, durability, and aesthetics
of the final FRP product, making it suitable for its intended application. Some
common finishing techniques used in pultrusion may include:
i.
Trimming and Cutting: After the pultruded profiles are cut to the desired
lengths using a cut-off saw, trimming and cutting operations may be
performed to remove irregular edges. This helps achieve precise dimensions and clean-cut ends if this was not previously achieved by the cut-off
saw.
ii.
Grinding and Sanding: Grinding and sanding processes are used to smooth
rough edges, remove potential imperfections, adjust the profile’s surface
finish or prepare the surface for a coating. This can be done manually or
using automated grinding and sanding equipment. The goal is to achieve
a consistent and smooth surface texture which will depend on the type of
element being manufactured and application.
iii.
Surface Treatment: Various surface treatments can be applied to FRP
pultruded elements. Surface treatment may be used to enhance performance, durability, and/or appearance. These treatments may include chemical cleaning, surface priming, or the application of coatings, paints, or gel
coats. Surface treatments can improve resistance to UV degradation, corrosion, or chemical exposure and enhance the overall aesthetics based on the
application of the FRP pultruded element.
iv.
Machining and Drilling: If the pultruded profiles require holes, slots, or
specific features, machining and drilling operations are performed. This
3. FRP PULTRUDED COMPONENTS: HOW 21
involves using cutting tools or machining equipment to create the required
openings or shape the profiles as per the design specifications.
v.
Assembly and Joining: Finishing in pultrusion may also involve assembly
and joining processes, where multiple pultruded elements or other components are combined to form larger structures. This can include bonding,
fastening, or chemical welding techniques, depending on the specific
requirements of the application. Many FRP composites can be assembled
in the manufacturing plant and transported to a designated site fully assembled, reducing on-site labor, time and costs.
vi.
Quality Inspection: Throughout the finishing stage, quality inspection is
typically conducted to ensure that the FRP pultruded elements meet the
required standards and specifications. Inspection may involve visual
inspection, dimensional measurement, mechanical testing, non-destructive testing, or other quality control processes. This document will further
discuss material specification and FRP product qualification.
Hence, to date the pultrusion process is characterized by a low labor and a high
raw material conversion efficiency for manufacturing continuous linear elements
with constant cross-sectional shapes with an attractive cost and consistent quality.
Moreover, the process is very versatile and may include an array of different
processes within the same production line. The process has acquired maturity, with
automatization and control systems developed to ensure high quality and consistency of engineering manufactured FRP elements. Pultrusion is now practiced
worldwide, becoming very competitive in the supply of a wide range of composites elements.
The pultrusion process can be considered more eco-friendly than traditional
manufacturing processes for some applications but it still has some environmental
impacts. Compared to traditional manufacturing methods, pultrusion uses less
energy, produces less waste, and emits fewer pollutants. However, pultrusion still
requires the use of raw materials such as fibers and resins that may have environmental impacts associated with their extraction and production. Additionally, some
of the resins used in pultrusion may contain volatile organic compounds (VOCs)
that can contribute to air pollution.
3.3 FIBERS IN FRP
The reinforcement materials or fibers in FRP pultruded elements provide strength,
stiffness, and other mechanical properties to the final pultruded composite. Thus,
the choice of fiber reinforcement materials depends on the specific performance
criteria required for the pultruded element being manufactured, such as strength,
stiffness, impact resistance, or corrosion resistance. By selecting the appropriate
reinforcement materials and optimizing their arrangement and fiber orientation,
pultruded elements can be tailored to meet a wide range of application needs in
various industries, as discussed in this document. In this section of the document
the key role of fiber reinforcement materials, orientation, as well as commonly
used fibers presented [10].
3.3.1 Role of Fibers
As the reinforcement material in FRP elements, the fiber’s primary role is to
carry the applied load that the pultruded element is subject to; whichever type
of load it may be (dead, live, thermal, dynamic, static…etc.). Thus, the derived
mechanical properties of a finished pultruded FRP element are a direction function
on the type of quantity of fibers within the element. To this end, depending on the
specific performance criteria required for the pultruded element and the design
requirements, the key role that fibers play in FRP elements include:
i.
Strength: Fibers contribute significantly to the strength of pultruded
elements, where fibers distribute and carry the applied loads, enhancing
the structural integrity and load-bearing capacity of the finished FRP
composite.
22
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
ii.
Stiffness: The fibers add stiffness and rigidity allowing the composite to
resist deformation and maintain its shape under load, resulting in improved
dimensional stability and structural performance.
iii.
Fatigue: Resistance: Fibers improve the fatigue resistance, where continuous fibers provide resistance against cyclic loading and prevent crack
propagation, making the composite more durable and long-lasting under
repetitive stress cycles.
iv.
Impact Resistance: Depending on the type of fiber and architecture (orientation) used in pultruded elements, it can improve impact resistance. Fibers
can enhance the ability of the composite to absorb and distribute impact
energy, reducing the risk of damage or failure upon impact.
v.
Corrosion Resistance: Fiber can also contribute to the corrosion resistance
of the overall FRP composite, making pultruded elements suitable for
applications in corrosive environments. The fibers act as a barrier against
chemical attack, moisture, and other corrosive agents, extending the service
life of the composite.
In general, the fiber content in pultruded profiles typically can range from 40%
to 70% by weight, where in certain applications this percentage can increase to
as high at 80 or 90%. Based on the role of the fibers in FRP composites, the fiber
content is a critical parameter that affects the mechanical properties. Ultimately, the
fiber content will vary based on factors such as the specific resin system, the type
and form of fiber (e.g., rovings, mats, fabrics), and the desired mechanical properties of the final product. Higher fiber content generally leads to increased strength
and stiffness of FRP pultruded elements. However, it’s important to balance the
fiber content with resin content to ensure proper impregnation, resin-to-fiber ratio,
and adequate consolidation during the pultrusion process as previously discussed.
The selection of the optimal fiber content in pultruded profiles involves considering factors such as the specific application requirements, processing considerations, cost constraints, and desired performance characteristics. Manufacturers
and engineers carefully evaluate these factors to determine the appropriate fiber
content to achieve the desired mechanical properties and overall performance of
the FRP pultruded composite.
3.3.2 Fiber Orientation
The orientation of the fibers in FRP pultruded elements plays a critical role in
determining the finished mechanical properties and performance characteristics.
Optimizing the fiber orientation in pultruded elements allows for tailoring the
mechanical properties to specific needs, such as maximizing strength, stiffness,
impact resistance, or a combination of these factors. This is a significant benefit of
FRP pultruded elements as it provides a wide range of design flexibility, allowing
for the creation of complex shapes, profiles, and customized structures. This is
because fibers can be oriented and arranged in multiple layers and arrays that meet
specific patterns or configurations to optimize the mechanical properties according
to the application requirements. Hence, by considering the fiber orientation,
pultruded elements can be engineered to meet the performance requirements of
diverse applications. In the end, the specific fiber orientation in pultruded elements
is determined by the design requirements and the anticipated loading conditions of
the final product. Manufacturers can achieve the desired fiber orientation through
various techniques, such as using different fiber forms of orientation as described
below or employing preforming processes to shape the fibers before impregnation.
It’s important to note that while specific fiber orientation provides unique strength
and stiffness for each given direction, it may have different properties in other
directions.
i.
Unidirectional: In unidirectional fiber orientation, the majority of the fibers
are aligned parallel to each other along the length of the pultruded element,
in the direction of pultrusion. Typically, the fibers are aligned along the
principal load-carrying direction, often referred to as the longitudinal direction. This arrangement provides high tensile strength and stiffness in the
3. FRP PULTRUDED COMPONENTS: HOW 23
ii.
iii.
iv.
direction of fiber alignment. Unidirectional reinforcement is commonly
used in applications where strength along the length is crucial, such as
structural members or load-bearing components.
Bidirectional: Bidirectional fiber orientation, also known as biaxial or twodirectional fiber orientation, refers to the arrangement of fibers aligned in
two primary directions: typically, longitudinally (along the length) and
transversely (across the width) relative to the pultruded element direction.
Additionally, the bidirectional orientation can also be at a relative angle
to the principal directions. This arrangement provides balanced strength
and stiffness in two directions, allowing for improved load distribution and
resistance to deformation, while it can also enhance the material’s shear
and torsional strength. Bidirectional reinforcement is often employed in
applications requiring isotropic properties, such as panels or sheets.
Multidirectional or Off-Axis: In multidirectional or off-axis fiber orientation, fibers are arranged in various directions, which may include the principal directions (longitudinal and transverse) as well as and intermediate
angles, to create a tailored reinforcement pattern. This allows for optimized
strength and stiffness in specific regions, segments of the pultruded element,
accommodating complex loading conditions and providing enhanced
structural performance. The multi-cross-ply arrangement can also help to
distribute and absorb impact energy in multiple directions, reducing the risk
of delamination or fracture upon impact type loads.
Three-Dimensional Fabrics: While to date FRP pultruded composite
elements are based on two-dimensional fiber orientation, which consist of
layer/s of fibers in the aforementioned orientations; the use of three-dimensional or 3D fabrics or textiles is being developed. 3D fabrics are composed
of multiple layers of fibers woven or braided together in three dimensions.
When pultruding 3D fabrics, these are typically impregnated with resin in
the resin bath before entering the die. The resin saturates the fibers within
the 3D fabric, and excess resin is squeezed out as the fabric passes through
the die. The pultrusion process then consolidates the impregnated 3D fabric
and cures the resin, resulting in a solid and fully cured pultruded composite
product. 3D fabrics provide reinforcement not only in the two-dimensional
plane but also in the thickness or z-direction of the pultruded composite.
This enhances the structural integrity and strength of the pultruded element
in all directions, including resistance against delamination and interlaminar
shear, as well as enhanced impact resistance, strength and stiffness.
3.3.3 Glass Fibers
Glass fibers are one of the most commonly used reinforcement materials in FRP
pultruded elements. Glass fibers are composed of thin strands of glass, typically
made from silica-based materials, that are drawn into fibers of various diameters.
These fibers provide excellent mechanical properties and are widely used in the
manufacturing of pultruded composite products.
At the end of the 18th century, glass fiber was first discovered by French scientist
Rene Ferchault de Reaumur, however little advancements were done with this first
discovery. In the late 19th century, glassmaking techniques underwent advancements that laid the foundation for the production of glass fibers. These advancements allowed for the creation of fine, flexible continuous glass filaments that
could be used for various applications. Over time, further research and development led to the refinement of glass fiber manufacturing processes, resulting in the
wide range of glass fibers we have today. Notably, in the 1930s, Owens-Corning
Fiberglas Corporation introduced the first commercially viable fiberglass insulation patenting ‘fiberglas’ as they discovered a process to produce air filters made of
glass fiber for ventilating equipment. These air filters were more efficient than the
cotton material used for the same purpose.
Today, glass fibers are considered to be most cost effective and significantly less
brittle as reinforcement than carbon in polymer composites. Glass fibers are made
24
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
from liquid, which is a melted ingredient with combinations of silica sand, limestone, fluorspar, kaolin clay, dolomite, colemanite, and other minerals. The certified chemical composition applied to glass fiber products used in general applications is provided in Figure 10, which is an extract from ASTM D578 Section 4.2.2,
the Standard Specification for Glass Fiber Strands (ASTM 2018). The melted glass
is extruded through metallic plates with multiple holes/tips called bushings to a
typical diameter of 5–25 μm. Individual fiber filaments are treated with a dedicated chemical solution, called sizing, to provide a protective coating before being
bundled together to form rovings. There are several types of glass fibers used in
pultrusion, each with its own specific properties and characteristics, where the
main types or categories of glass fibers are described below. Other types of glass
fibers exist.
Overall, the main advantages of glass fibers as seen in Figure 11 are corrosion
resistance, low cost, and relatively high tensile strength, while some of the disadvantages include a relatively low stiffness compared to other fibers like carbon,
fatigue endurance, and degradation with severe hygrothermal environments, i.e.,
strength loss under load, heat and moisture [10].
i.
E-Glass: Electrical Glass or E-Glass fibers are the most widely used type of
fiber in pultrusion when exceptional corrosion resistance is not a required
specification for the FRP application. E-Glass alumino-borosilicate glass
with less than 1% in mass of alkali oxides. It offers good mechanical properties, including high tensile strength and stiffness. E-Glass fibers also
provide excellent electrical insulation properties, making them suitable for
applications requiring electrical non-conductivity.
ii.
E-CR Glass: Electrical Corrosion Resistant Glass fibers (also known
as Advantex® glass fiber) are a type of boron free glass fiber that offers
improved corrosion resistance compared to traditional E-Glass fibers.
E-CR glass is alumino-lime silicate with less than 1% in mass of alkali
oxides and offers comparable mechanical and electrical insulation properties to traditional E-Glass fibers. E-CR glass is designed to withstand
long term exposure to acids, and short term to alkalis, and other corrosive
substances, making them suitable for applications where chemical resistance is a critical requirement.
iii.
S-Glass: Structural Glass or S-Glass fibers exhibit higher strength and stiffness compared to E-Glass fibers. S-Glass is alumino silicate glass without
CaO but with high MgO content, and has superior mechanical properties,
particularly in terms of tensile strength, impact resistance, and fatigue
resistance. S-Glass fibers are commonly used in applications that demand
higher performance and structural integrity, such as aerospace and military
applications.
iv.
C-Glass: Chemical Glass or C-Glass fibers are designed to have enhanced
chemical resistance. It is a alkali-lime glass with high boron oxide content,
used primarily for glass staple fibers and insulation. They exhibit good
resistance to chemical corrosion, making them suitable for applications in
aggressive chemical environments.
v..AR-Glass (Alkali-Resistant Glass):
AR-Glass fibers are specially formulated to resist the effects of alkaline
substances as this is a alkali-lime
glass with little or no boron oxide.
They are commonly used in applications where the composite material is
exposed to alkaline environments.
Figure 10 – Certified chemical composition applied to glass fiber products used in
general applications, per ASTM D578
3.3.4 Carbon Fibers
Typically, carbon fiber contains at
least 90% of carbon by weight. The
most common raw materials used on
3. FRP PULTRUDED COMPONENTS: HOW 25
carbon fibers include polyacrylonitrile
(PAN), petroleum or coal tar pitch,
etc. Carbon fibers are produced from
synthetic polymers (such as PAN)
spun into filament yarns. Carbon
fibers are finished by heating and
stretching treatment through chemical and mechanical processes. Typically, the filament of carbon fiber has
a diameter of 5–10 μm. The overall
characteristics of carbon fibers
include high tensile strength to weight
Figure 11 – Glass fiber in roving (left) and fiber fabric (right) ref: [10]
ratio, high tensile stiffness to weight
ratio, high fatigue, toughness, and
stress rupture resistance, high-dimensional stability, low abrasion, low coefficient
of thermal expansion, good vibration damping, and high corrosion resistance and
chemical inertness. It is worth noting that carbon fibers have a significant higher
cost, brittleness, and are electrically conductive, with electromagnetic properties,
when compared to the other available fiber used for FRP pultrusion, hence limiting
their potential use in some applications.
Carbon fibers date back to the late 1950s where Dr. Roger Bacon at Union
Carbide’s Parma Technical Center in the United States began experimenting with
carbon fibers. He discovered that carbon fibers could be produced by heating organic
fibers, such as rayon or PAN, to high temperatures in an inert atmosphere, which
resulted in the carbonization of the fibers. Soon after this, in the early 1960s, Union
Carbide commercialized the first carbon fibers under the brand name “Thornel.”
These early carbon fibers were derived from rayon precursors and had limited
mechanical properties. They were primarily used as reinforcement in specialty
aerospace applications. It was not until the mid 1960s when Dr. Akio Shindo at
Nippon Carbon and Dr. Yoshihiro Takeda at the National Research Institute for
Chemical Fibers (Japan) independently discovered that PAN fibers could be used
as a precursor for carbon fibers, offering superior mechanical properties compared
to rayon-based fibers. In the 1970s, researchers at Union Carbide (later acquired
by Amoco) and Hercules Aerospace (later acquired by Hexcel) developed highstrength carbon fibers by optimizing the precursor material (PAN), the stabilization
process, and the carbonization process. These advancements resulted in carbon
fibers with higher tensile strength and modulus. For the next decade carbon fibers
gained significant attention and implementation in the aerospace industry. The high
strength, stiffness, and lightweight properties of carbon fibers made them suitable
for structural components in aircraft, such as wings, fuselage sections, and rotor
blades. Over the years, continued research and development efforts by numerous
companies and institutions around the world have led to further advancements in
carbon fiber technology. This includes improvements in fiber strength, modulus,
and manufacturing processes.
Carbon fibers as seen in Figure 12, are now available in various grades, offering
a wide range of properties to suit different applications. There are several types of
carbon fibers available, and their characteristics vary depending on factors such as
manufacturing process, precursor material, and treatment methods. Here are the
primary types of carbon fibers in used to date:
i.
Pitch-Based: Pitch-based carbon fibers are derived from petroleum or coal
tar pitches. They have a higher carbon content and can achieve high tensile
strength and stiffness. Pitch-based fibers are often used in applications
requiring high thermal and electrical conductivity, such as in the aerospace
and automotive industries.
ii.
PAN-Based: Polyacrylonitrile-based (PAN) carbon fibers are the most
commonly used type of carbon fibers. They are manufactured from PAN
precursor materials and can be processed to provide a wide range of properties based on the manufacturing conditions and treatments applied.
26
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Carbon fibers are then categorized
based on the modulus, as follows:
i..Standard
Modulus:
Standard
modulus carbon fibers have a relatively lower tensile strength and
stiffness compared to other carbon
fiber types. They are commonly used
in general applications that require
good mechanical properties and a
balance between performance and
cost such as the construction and built
Figure 12 – Carbon fiber in roving (left) and fiber sheet (right) ref: [10]
environment.
ii.
Intermediate Modulus: Intermediate modulus carbon fibers offer higher
tensile strength and stiffness compared to standard modulus fibers. They
provide improved performance characteristics and are often used in applications where higher strength and rigidity are required, such as aerospace
components and sporting goods.
iii.
High Modulus: High modulus carbon fibers exhibit exceptional tensile
strength and stiffness. They are designed to provide the highest level of
performance and are used in demanding applications, including aerospace,
high-performance sporting equipment, and advanced structural composites, such as strengthening or repair of existing built infrastructure.
iv.
Ultra-High Modulus: Ultra-high modulus carbon fibers possess extremely
high tensile strength and stiffness. They offer the highest levels of performance but also more expensive. These fibers find application in specialized
industries such as aerospace, defense, and high-end sporting equipment.
It’s important to note that within each carbon fiber category, further customization can be provided by adjusting the manufacturing process such as the carbonization temperature, tension during processing, and surface treatment methods. This
allows FRP pultruded manufacturers to tailor the properties of carbon fibers to
suit specific pultruded element applications. Ultimately, the selection of the appropriate carbon fiber type depends on the requirements of the application, including
strength, stiffness, weight, cost, and other performance and design factors.
3.3.5 Basalt Fibers
Basalt fibers are a type of synthetic fiber made from the naturally occurring
volcanic basalt rock. Basalt rock is an aphanitic extrusive igneous rock formed
from the rapid cooling of low-viscosity lava rich in magnesium and iron exposed
at or very near the surface.
The history of commercially available basalt fibers is relatively more recent
compared to other fiber types. Researchers and engineers recognized the potential of basalt as a raw material for fiber production due to its abundance, high
melting point, and excellent mechanical properties for industrial applications
around the 1920s and 1930s. Nevertheless, it was not until the 1950s and 1960s
when significant developments in basalt fiber technology took place in the former
Soviet Union. Researchers at the Kiev Polytechnic Institute and the Ukrainian
Academy of Sciences began investigating methods to produce basalt fibers on
an industrial scale. In the 1970s, basalt fiber production lines were established in
Ukraine and other Soviet Union countries while using a similar process to glass
fiber manufacturing with basalt rock being melted at high temperatures and then
extruded into fibers. Soon after that, basalt fibers started being commercialized
on a larger scale in the 1980s. Basalt fiber products were initially used in military and aerospace applications while taking advantage of their high strength, fire
resistance, and thermal insulation properties. Following the collapse of the Soviet
Union, basalt fiber production gradually expanded globally which led to increased
availability and application of basalt fibers in different industries. Over the years,
advancements have been made in basalt fiber production techniques, resulting in
improved fiber quality and performance. Commercial production of basalt fibers
3. FRP PULTRUDED COMPONENTS: HOW 27
has continued to evolve, with ongoing
research and development efforts
focusing on optimizing the manufacturing process, enhancing fiber properties, and exploring new applications.
To manufacture basalt fibers, only
basalt rock is needed (without chemicals or other additives unlike the other
fibers discussed in this document).
This may make it more sustainable
due to the single raw material dependance. To produce basalt fibers, basalt
needs to be extracted from quarries,
crushed, washed, and melted at about
Figure 13 – Basalt fiber products
1350C in a furnace similar to the ones
used within the glass fiber industry.
The molten basalt is then extruded
through metallic bushings (plates with
multiple small holes) and the extruded
fiber is sprayed with the coating or
sizing.
While discrete basalt fibers (also
known as chopped or short basalt
fibers) are available in shorter lengths
Figure 14 – Primary chemical composition of basalt fiber products
typically ranging from a few millimeters to several centimeters, in pultrusion, continuous basalt fibers (also referred to as CBF) are the main type of basalt
fiber designation (see basalt fiber product examples in Figure 13). To date there are
no standardized categories of basalt fibers, where the primary chemical composition of basalt fiber products is provided in Figure 14, based on ASTM D8448, Standard Specification for Basalt Fiber Strands (ASTM 2022). Continuous basalt fibers
have a high aspect ratio (length-to-diameter ratio), offering excellent mechanical
properties. Compared to other fibers like glass fibers, basalt fibers have a relatively
higher stiffness (modulus of elasticity), tensile strength, and heat resistance. Thus,
their use is increasing exponentially.
3.3.6 Aramid Fibers
Aromatic polyamide fibers, or aramid for short, see Figure 15, are a class of
heat-resistant and strong synthetic fibers which are manufactured as long synthetic
polyamide chains. At least 85% of the amide linkages are attached directly to two
aromatic rings [11]. It is the most common polymer fiber used in FRP pultruded
elements; other polymer fibers are included in Section 3.3.7.
Aramid fibers have higher strength and stiffness-to weight ratios when compared
to glass fibers. Aramid fibers offer excellent toughness and impact resistance. In
addition, the mechanical response of aramid fibers under impact loading tends to
be ductile when compared with carbon fibers.
The development and commercialization of aramid fibers can be attributed to the
research and innovation of two major companies: DuPont and Teijin. In the 1960s,
a team of researchers at DuPont, led by Stephanie Kwolek, were working on developing new polymers for tire reinforcement. During their experiments, they discovered a new class of synthetic fibers with exceptional strength and heat resistance,
drawing upon their knowledge of rayon, polyester, and nylon processing. The
first commercial applications of aramid fibers occurred in the early 1960s when
DuPont produced met-aramid fibers known as ‘HT-1.’ This fiber was characterized
by its excellent resistance to heat, as it neither melts nor ignites in normal levels of
oxygen. In 1965, DuPont introduced the first commercially available aramid fiber
under the brand name Nomex®. Building on the success of Nomex®, DuPont
continued its research and development efforts in the field of aramid fibers and in
28
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Figure 15 – Aramid fiber products
the early 1970s introduced Kevlar®,
a para-aramid fiber that surpassed
Nomex® in terms of strength and
rigidity. Meanwhile, in Japan, the
Teijin company was also working on
the development of aramid fibers. In
1972, Teijin successfully commercialized its own para-aramid fiber known
as Twaron® (sharing similar properties with Kevlar®).
Kevlar and Twaron are manufactured from a condensation reaction of para-phenylenediamine and
terephtheloyl chloride. The formation of aromatic ring structures and
para configurations contributes to
high strength, modulus, and thermal
stability. The main characteristics of aramid fibers are summarized as low flammability , no melting point, very high damping coefficient, high strength and modulus
with a slightly different molecular structure, good fabric integrity at elevated
temperatures, very low thermal conductivity, high impact, and dynamic load resistance. While there are several types of aramid fibers available to date, the two most
common ones include meta-aramid and para-aramid fibers, which both offer excellent resistance to organic solvents and chemicals:
i.
Meta-Aramid: Meta-aramid fibers are typically represented by the brand
name Nomex®, while other manufacturers may produce meta-aramid
fibers under different brand names too. These fibers are produced from poly
meta-phenylene isophthalamide (PMIA) polymer. These fibers offer high
strength and thermal stability, making them suitable for applications where
heat and flame resistance are required. They have a high melting point and
do not melt or drip when exposed to fire. Meta-aramid fibers are commonly
used in protective clothing, such as firefighter gear, industrial workwear,
and electrical infrastructure insulation applications.
ii.
Para-Aramid: Para-aramid fibers are best known by the brand name
Kevlar®, while other manufacturers may produce para-aramid fibers
under different brand names as well. These fibers are made from poly paraphenylene terephthalamide (PPTA) polymer. Para-aramid fibers possess
exceptional tensile strength and modulus, making them among the strongest synthetic fibers available. They also exhibit high resistance to impact,
cuts, and abrasion. Para-aramid fibers are widely used in ballistic protection, such as bulletproof vests, helmets, and armor, as well as in aerospace,
automotive, and industrial applications where high-strength is a design
requirement.
3.3.7 Other Polymer Fibers
Polymer fibers are a significant reinforcement material in FRP pultruded
elements. These fibers, composed of long chains of polymers, can be tailored to
specific diameters and properties. Offering a combination of flexibility, strength,
and chemical resistance, polymer fibers are suitable for various composite products. Even if aramid is the most frequently used polymer fiber in FRP pultruded
elements (covered in Section 3.3.6), other polymer fibers exist and are used in
the manufacturing of pultruded elements. The development of synthetic polymer
fibers, such as nylon and polyester, began in the early 20th century and revolutionized textiles and industrial composites. In the 1930s, the DuPont company’s
introduction of nylon laid the groundwork for further advancements in polymer
fiber technology.
Today, polymer fibers are manufactured using various synthetic materials,
including polyethylene and polypropylene. The production process typically
3. FRP PULTRUDED COMPONENTS: HOW 29
involves the extrusion of melted polymer through spinnerets, followed by drawing
and cooling to form fibers with diameters ranging from 10–50 μm. These fibers are
often treated with specific coatings or sizing to enhance their bonding with resin
matrices. In addition to aramid fibers (covered in Section 3.3.6), the main types or
categories used in pultrusion are described below:
i.
Nylon: In FRP pultruded materials, nylon fibers contribute tensile strength
and elasticity. Their resistance to abrasion and environmental conditions
makes them suitable for various structural applications. Nylon’s adaptability in FRP pultrusion enhances durability and flexibility, making it a
valuable reinforcement material in construction and industrial composites.
ii.
Polyester: Polyester fibers are used in FRP pultruded materials for their
balance of strength, flexibility, and resistance to chemicals and UV radiation. Their application in outdoor and structural composites ensures
long-term performance and integrity. Polyester’s unique properties make
it a preferred choice for reinforcing FRP pultruded elements in diverse
environments.
iii.
Polyethylene (PE): Polyethylene fibers, including HDPE and UHMWPE,
offer lightweight strength in FRP pultruded materials. Their high tensile
strength is utilized in demanding applications, such as aerospace and
advanced construction. In FRP pultrusion, polyethylene fibers provide
innovative solutions, meeting specific performance requirements and
contributing to the efficiency of modern design and manufacturing.
Overall, the main advantages of these polymer fibers include their versatility
in properties, lightweight nature, and resistance to corrosion and environmental
degradation. Some of the disadvantages may include sensitivity to UV radiation (in
certain types), cost considerations, and specific mechanical properties compared
to other fibers like glass. These polymer fibers continue to evolve, with ongoing
research and development focusing on enhancing their properties and expanding
their applications. In the context of FRP pultruded elements, these fibers offer a
range of options to meet specific design and performance requirements, contributing to the innovation and efficiency of modern construction practices.
3.4 SIZING IN FRP
Fiber sizing, also known as fiber finish, sizing agent or coating, is a specialized layer applied to individual fiber filaments used in FRP pultruded composites
and applies to all fibers including carbon, glass, basalt, aramid, and other types of
fibers. It is a crucial component in the manufacturing process of dry unsaturated
fibers, serving multiple functions and playing a significant role in the performance
of the final FRP pultruded manufactured composite.
Fiber sizing is typically applied during the manufacturing process of the dry
fibers and hence it is a component of the dry fiber. Nevertheless, sizing can also
be added later as a separate step before the fabrication of a FRP composite. The
primary purpose of fiber sizing is to enhance the bond between the fibers and the
resin matrix material. Thus, the sizing acts as an interface between the fiber surface
and the resin, improving adhesion and transferring stress between the two materials. As a result, the sizing distributes the load more evenly across the composite
and prevents premature fiber failure or debonding. Moreover, the functions of the
fiber sizing include:
i.
Protection: Fiber sizing provides a protective layer on the surface of the
fiber, which prevents damage or degradation during the handling and
processing of the dry fiber (e.g. while setting it up in the spools for pultrusion), as well as protection from exposure to environmental factors.
ii.
Adhesion: As previously mentioned, the primary purpose of fiber sizing is
to improve the bonding between the fiber and the resin matrix. It enhances
the wetting and adhesion characteristics of the fiber surface, ensuring efficient load transfer and stress distribution between the fiber and the resin
matrix in the cured FRP composite.
30
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
iii.
Compatibility: Sizing agents are specifically designed to match the properties of the fiber and the resin saturating the fibers, optimizing compatibility between the two materials for the given FRP composite. This helps
to minimize issues such as fiber-resin debonding, delamination, or weak
interfacial bonding, that can cause premature and undesired failures of the
composite when in service.
iv.
Lubrication: Fiber sizing often includes lubricants or surfactants that reduce
friction during processing, improving the handling and flow properties of
the fibers. This facilitates the impregnation of the fibers with the resin and
reduces the risk of fiber breakage or damage while the pultrusion process is
underway, ensuring quality and consistency of the FRP composite.
v.
Surface: Sizing can also function to modify the surface properties of the
fibers, such as roughness or energy, to achieve better adhesion and compatibility with specific resin systems.
vi.
Properties: Lastly, sizing has been also formulated to improve specific
aspects of the FRP pultruded elements such as toughness and strength due
to improved fiber surface adhesion and activation.
To achieve optimal mechanical properties, durability, and overall performance of
finished FRP pultruded composites, proper selection and application of fiber sizing
are critical. Pultruders must therefore select fiber + sizing + resin (as discussed
in the next section) combination that best meets the manufacturing, mechanical,
design and exposure needs in a holistic approach.
3.5 RESIN IN FRP
FRP elements made via pultrusion can be made with a variety of different resins
depending on the intended application as well as manufacturing process specifications, such as process times. As learned in this Chapter the selection of the resin
will also depend on the type of fiber and sizing to ensure adequate compatibility.
3.5.1 Role of Resin
In the FRP pultrusion process, resins play a crucial role as they serve as the
matrix material that not only binds the reinforcement fibers together to provide the
desired mechanical properties, but also plays a critical role to provide the desired
durability of the pultruded element for its intended use. To this end, depending on
the specific performance criteria required for the pultruded element and the design
requirements, the key aspects of resins in FRP elements include:
i.
Matrix: Resins essentially form the matrix material of FRP elements in
which the fibers are embedded. As a matrix, it needs to form and provide
a continuous phase that surrounds and supports all the fibers, providing
cohesion and structural integrity to the pultruded element.
ii.
Adhesion: Resins help improve the adhesion between the fibers and the
matrix material. Thus, the role as a bonding agent ensures a strong interface between the fibers and the matrix, enhancing the overall mechanical
properties of the pultruded product.
iii.
Mechanical Properties: While resins are not the primary load carrying
element of FRP pultruded elements, resins contribute to the mechanical
properties of the pultruded element. Different types of resins exhibit
varying levels of strength, stiffness, impact resistance, and other mechanical characteristics achieving the desired mechanical performance of the
final product. Additionally, the resin will be transferring and distributing
the load within the FRP element to the fibers.
iv.
Environmental Resistance: Resins provide protection and resistance to
environmental factors of the in-service FRP elements, such as moisture,
chemicals, UV radiation, and temperature variations, amongst others. The
choice of resin can be tailored to specific environmental conditions to
ensure long-term durability and performance of the pultruded product in
its intended application.
3. FRP PULTRUDED COMPONENTS: HOW 31
v.
Curing and Hardening: Resins undergo a curing process during pultrusion,
where they are chemically transformed from a liquid or semi-liquid state to
a solid state. As discussed previously, this curing process can be achieved
through heat, pressure, chemical reactions, or a combination thereof.
Curing ensures that the resin hardens and securely bonds the reinforcement
fibers together, resulting in a rigid and durable pultruded element.
vi.
Processing and Flow: Resins with appropriate viscosity and flow properties facilitate the pultrusion process. Resin needs to flow through the die
and impregnate all the fibers effectively and consistently. The viscosity
of the resin must therefore be formulated and controlled to ensure proper
wetting and impregnation of the fibers while maintaining a manageable
pultrusion processing temperature.
Ultimately, the choice of resin depends on several factors, including the desired
mechanical properties, environmental conditions, chemical resistance requirements, manufacturing setup and process requirements, as well as cost considerations. It is essential to select the appropriate resin system to ensure that the
pultruded elements meet the specific performance requirements of the intended
application.
3.5.2 Themoset vs. Themoplastic
Thermoset and thermoplastic are two distinct categories of polymers that differ
in their behavior when exposed to heat and curing processes. While pultrusion is
traditionally associated with thermosetting resins (such as polyester, vinyl ester,
and epoxy), there has been increasing interest in utilizing thermoplastic resins
for pultrusion processes. The use of thermoplastics in pultrusion can offer certain
advantages, including faster processing times, improved recyclability, and the
ability to reshape or reform the material after processing, which can be ideal for
certain applications.
Thermoset resins undergo a one-way chemical curing process to form a rigid and
crosslinked structure. Once cured, thermoset resins cannot be melted or reformed
by heating, as they undergo irreversible chemical reactions that result in a threedimensional network of polymer chains. This curing process, often triggered by
heat or a combination of heat and catalysts, transforms the resin from a liquid or
semi-liquid state into a solid, infusible material.
Thermoplastic resins can be repeatedly melted and solidified without undergoing
significant chemical changes. They have a unique property of becoming soft and
pliable when heated and returning to a solid state upon cooling. Unlike thermosetting resins, which undergo irreversible chemical crosslinking upon curing, thermoplastic resins can be melted and reshaped multiple times, making them recyclable
and allowing for efficient processing.
The primary differences between thermoplastics and thermosets are descried
below:
i.
Molecular Structure: Thermosets have a three-dimensional crosslinked
structure due to chemical reactions during curing. Once cured, it becomes
permanently rigid and cannot be melted or reformed without undergoing
degradation. Thermoplastics, however, are composed of long, linear chains
of polymers that are entangled but not chemically crosslinked. This allows
it to soften when heated and solidify when cooled repeatedly without
undergoing significant chemical changes.
ii.
Melting and Processing: Thermosets undergo irreversible chemical crosslinking during the curing process and do not melt upon heating. Once
cured, it retains its shape and cannot be reprocessed by melting. Thermoplastics, however, have a distinct melting point and can be melted and
reshaped multiple times without degradation. This property allows for easy
processing for other manufacturing methods such as injection molding,
extrusion, and thermoforming.
iii.
Curing Process: Thermosets require a curing process to transform from a
liquid or semi-liquid state to a solid, crosslinked state. This curing process
32
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
is typically triggered by heat, pressure, and/or chemical reactions and is
irreversible. While thermoplastics do not require a curing process as it
solidifies upon cooling after being melted.
iv.
Mechanical Properties: Thermosets, once cured, have higher strength,
stiffness, and dimensional stability. Hence, it is often preferred for applications requiring excellent mechanical properties and resistance to heat
and chemicals. Thermoplastics tend to have lower strength and stiffness
compared to thermosets, but can exhibit good impact resistance, flexibility,
and toughness.
v.
Recycling and Sustainability: Thermosets, due to their irreversible crosslinked structure, are more challenging to recycle. Current advances in
recycling technologies are being made to address the recycling of thermoset materials. Thermoplastics are generally more recyclable compared
to thermosets due to the ability to be melted and reshaped multiple times,
allowing for recycling and reusing the material.
The choice between thermoplastic and thermoset polymers depends on the
specific requirements of the application. Thermoplastics are often chosen for their
versatility, ease of processing, and recyclability, while thermosets are preferred
for their superior mechanical properties and resistance to heat and chemicals. The
following section of this document provides an overview of the primary resins
(both thermosets and thermoplastics) for FRP pultruded applications.
3.5.3 Epoxy
Epoxy resin is a type of thermosetting resin that is widely used in the pultrusion industry for its excellent adhesion, high strength, and chemical resistance.
It is created through the reaction of epoxide monomers with a curing agent,
commonly referred to as a hardener. The curing process involves a chemical reaction that results in the formation of a crosslinked network, giving epoxy resin its
unique properties. Epoxy is one of the higher performing (and higher priced) resin
systems. It is used in weight critical, high strength, and dimensionally accurate
applications. Epoxy resin-based pultruded elements can exhibit outstanding stiffness, dimensional stability, and fatigue resistance.
To date, the primary characteristics and applications of epoxy resin include its
exceptional adhesion to a wide range of substrates (including metals, concrete,
wood, and other composites). This property makes it suitable for applications
where strong bonding and structural integrity are required, such as in construction, aerospace, automotive, and marine industries. Epoxy resins also possess high
mechanical strength and stiffness, making them suitable for providing structural
support and resistance to deformation. They are also commonly used in applications where load-bearing capabilities are essential, including composite materials,
structural adhesives, and FRP components. Furthermore, epoxy provides excellent
resistance to many chemicals such as acids, bases, solvents, and oils. This chemical
resistance makes it suitable for use in industrial environments, corrosion protection
coatings, chemical storage tanks, and chemical-resistant flooring systems. Thus, it
is often used as a protective coating for surfaces due to its durability and ability to
adhere to different substrates. It is commonly applied as floor coatings, concrete
sealants, protective coatings for metals, and corrosion-resistant coatings. Furthermore, epoxy resins are an effective electrical insulator, used in the production of
circuit boards, electrical encapsulation, transformers, and insulating coatings. In
general, epoxy resin can be customized to meet specific application requirements
by selecting the appropriate resin formulation system, hardener, and additives. This
allows for the achievement of specific properties and performance characteristics.
It can be filled with additives such as fillers, fibers, and pigments to enhance its
mechanical properties, electrical conductivity, or aesthetics.
3.5.4 Polyester and Isophthalic Polyester
Polyester resin is a widely used type of thermosetting resin. It is cost-effective,
has good mechanical properties, and provides resistance to corrosion and chemi-
3. FRP PULTRUDED COMPONENTS: HOW 33
cals. Polyester resin is commonly used in applications where high strength and
stiffness are not the primary requirements. It is formed through the reaction of
unsaturated dibasic acids (such as maleic or phthalic acid) with polyhydric alcohols (such as ethylene glycol), resulting in a polyester polymer.
Isophthalic polyester is one of the most widely used resins in pultrusion for its
versatility, affordability, and ease of use. It also has several advantages over standard polyester resin, including improved chemical resistance, thermal stability, and
resistance to water absorption. It is commonly used in applications where enhanced
corrosion resistance and durability are required, except for use in environments
exposed to alkaline substances. It is one of the most commonly used polymers for
structural composites due to its low cost.
Some key attributes of isophthalic polyester resin include the excellent chemical
and corrosion resistance to a wide range of chemicals, including acids, solvents,
and corrosive substances. Isophthalic polyester resin offers improved thermal
stability compared to regular polyester resin, as it can withstand higher temperatures without deforming or losing its structural integrity. It also has lower water
absorption properties compared to standard polyester resin. This makes it less
prone to swelling or degradation when exposed to moisture or humid conditions.
Hence it is commonly used in marine applications, water tanks, and other applications where water resistance is important. To this end, isophthalic polyester resin
finds applications in various industries, including chemical processing, infrastructure, transportation, marine, and electrical. It is used in the production of corrosionresistant composites, coatings, adhesives, and laminates.
3.5.5 Vinyl Ester
Vinyl ester resin is a type of thermosetting resin that is derived from the esterification of epoxy resin with unsaturated monocarboxylic acid, typically methacrylic
acid. This resin combines the properties of epoxy resin and polyester resin, offering
improved chemical resistance and toughness compared to standard polyester resins.
Vinyl ester resin is known for its high corrosion resistance, strength, and durability,
making it suitable for various demanding applications.
Vinyl ester offers excellent chemical and corrosion resistance to a wide range of
chemicals including acids, alkalis, organic solvents, and corrosive environments.
This property makes it suitable for applications where resistance to a chemical
attack is crucial, such as in chemical processing equipment, storage tanks, and
pipes. It is also an ideal choice for applications in aggressive environments, such as
marine, offshore, and industrial settings. It is used in the construction of corrosionresistant structures, including grating, handrails, and structural components. Vinyl
ester also offers high mechanical strength and toughness, providing structural
integrity and impact resistance, along with good dimensional stability, maintaining
its shape and properties over a wide temperature range. Furthermore, vinyl ester
can be formulated to exhibit good fire-resistant properties, meeting fire safety regulations and standards. This makes it suitable for applications where fire resistance
is required, such as in transportation, construction, and electrical enclosures. Vinyl
ester resin can be applied in various industries, including chemical processing, oil
and gas, marine and offshore, infrastructure, automotive, and aerospace. It is used
in the production of corrosion-resistant composites, coatings, adhesives, and repair
material and is a cost-effective resin system.
3.5.6 Polyurethane
Polyurethane resin is a versatile type of thermosetting resin that is derived from
the reaction of polyisocyanates with polyols. It is known for its excellent mechanical properties, durability, and versatility in various applications. Polyurethane
resin can be formulated into different forms, including liquid resins, foams, and
elastomers, offering a wide range of properties and applications. This resin has
high strength and impact damage tolerance. Polyurethane resin is used in specific
pultrusion applications that require exceptional toughness, flexibility, and impact
resistance. It offers good resistance to abrasion, making it suitable for applications
34
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
where durability and resistance to environmental conditions are critical. Aromatic
polyurethanes are susceptible to UV degradation, therefore secondary UV protection is required for outdoor applications. Aliphatic polyurethanes perform well in
outdoor applications.
The versatility of polyurethane resin is a key attribute, as it can be formulated into
various forms such as liquid resins, foams, and elastomers, offering a wide range
of properties and applications. Additionally, it can be tailored to exhibit different
levels of hardness, flexibility, or rigidity, depending on the desired application.
Polyurethane resin is also known for its excellent mechanical properties, including
high strength, toughness, and impact resistance. It can withstand heavy loads and
resist deformation, making it suitable for applications that require durable and reliable materials, such as automotive parts, industrial components, and construction
materials. Also, this resin exhibits good resistance to many chemicals, including
oils, solvents, and various industrial chemicals. Polyurethane resin has excellent
adhesion properties, enabling it to bond well with various substrates, including
metals, plastics, and fabrics; while exhibiting good thermal stability, with the
ability to withstand a wide range of temperatures without significant degradation.
This property makes it suitable for applications that involve exposure to high or
low temperatures such as in insulation materials and electronic components. The
specific properties of polyurethane resin can vary depending on the formulation
and additives used. This allows for customization and tailoring of the resin formulation to meet the specific requirements of different applications.
In general, polyurethane resin finds applications in a wide range of industries,
including automotive, construction, aerospace, furniture, footwear, coatings, and
adhesives. It is used in the production of various products, including foams, elastomers, coatings, sealants, and flexible or rigid components.
3.5.7 Phenolic
Phenolic resin is a type of synthetic thermosetting resin that is derived from
the reaction of phenol (or substituted phenols) with formaldehyde. Phenolic resin
offers several unique properties that make it suitable for a wide range of applications. For electronics, ballistics, mining, and other high-temperature applications,
phenolic resins are flame retardant, non-combustible, resistant to chemicals, and
electrically non-conductive. It is widely used in underground infrastructure where
fire safety is critical.
High temperature resistance is one of the key characteristics of phenolic resin
making it suitable for applications that involve high temperatures. It can withstand
temperatures up to 200 - 250°C (392 - 482°F) without significant degradation.
Additionally, phenolic resin is inherently flame retardant and offers excellent fire
resistance. It has low smoke and toxicity emissions when exposed to fire, making
it valuable for applications where fire safety is a concern, such as in building
materials, electrical components, and transportation. Phenolic resin provides good
mechanical strength and rigidity, as it has high compressive strength and is resistant to impact and deformation, making it suitable for load-bearing applications.
Phenolic resins are commonly used composites for structural components, friction
materials, and abrasive applications. Overall, phenolic resins can provide good
resistance to various chemicals, can provide excellent electrical insulation, and
have good dimensional stability. To this end, phenolic resin finds applications in
various industries, including automotive, aerospace, construction, electrical, and
consumer goods. It is used in the production of composite materials, molded parts,
coatings, adhesives, insulation materials, and friction components.
3.5.8 Acrylic
Acrylic resin refers to a group of thermoplastic resins derived from acrylic acid
or methacrylic acid. These resins are commonly known as polymethyl methacrylate (PMMA) or simply acrylic. Acrylic resins are widely used in various industries
due to their desirable properties, including transparency, weatherability, impact
resistance, and ease of processing.
3. FRP PULTRUDED COMPONENTS: HOW 35
Acrylic resins have excellent transparency, allowing for high light transmission.
It also has good optical clarity, making it suitable for applications that require
clear and transparent materials, such as windows, skylights, displays, and signage.
Furthermore, acrylics exhibit excellent weather resistance, retaining their transparency and color stability even when exposed to sunlight and outdoor conditions. Additionally, they offer good impact resistance, making it less prone to
shattering compared to glass. This property makes it suitable for applications that
require impact-resistant materials, such as safety glazing, protective shields, and
helmet visors. Nevertheless, it is the resistance to many chemicals, including acids,
alkalis, and solvents that is the reason for acrylics being considered for pultrusion applications such as concrete reinforcement bar due to its ease to be molded
into various shapes and sizes, allowing for versatile manufacturing possibilities.
However, acrylics may be sensitive to some organic solvents so compatibility
should be considered in specific applications.
3.5.9 Other Thermoplastics
The adoption of thermoplastic resins in pultrusion is still relatively limited
compared to thermosetting resins. The processing conditions and equipment for
thermoplastic pultrusion may differ from those used for thermosetting pultrusion.
Nevertheless, ongoing research, development, and advancements are focused on
optimizing the pultrusion process for thermoplastic resins and expanding their
application range. To this end, the use of thermoplastics in pultrusion can offer
certain advantages, including faster processing times, improved recyclability, and
the ability to reshape or reform the material after processing. Some thermoplastic
resins that have been explored for pultrusion applications are described below.
i.
Polypropylene (PP): Polypropylene is a versatile thermoplastic resin that
offers good mechanical properties, chemical resistance, and low density. It
has been used in pultrusion processes for applications where cost-effectiveness and lightweight properties are important, such as in the automotive
industry.
ii.
Polyamide (PA): Polyamide, commonly known as nylon, is a strong and
durable thermoplastic resin with good mechanical properties and chemical
resistance. It has been used in pultrusion for applications requiring high
strength and toughness, such as structural components.
iii.
Polyethylene (PE): Polyethylene is a widely used thermoplastic resin with
excellent chemical resistance, low cost, and versatility. It has been utilized
in pultrusion for applications where corrosion resistance and low weight
are critical, such as in the construction industry.
iv.
Polyvinyl Chloride (PVC): Polyvinyl chloride is a thermoplastic resin
known for its durability, electrical insulation properties, and chemical
resistance. It has been employed in pultrusion for applications such as
window profiles and electrical components.
v.
Polyphenylene Sulfide (PPS): Polyphenylene sulfide is a high-performance
thermoplastic resin with excellent chemical resistance, high temperature
resistance, and dimensional stability. It has been used in pultrusion for
applications requiring superior heat resistance, such as in the aerospace
and electrical industries
36
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
4. FRP PULTRUDED COMPONENTS: WHERE
The constituent materials used in the manufacturing of FRP pultruded composites, as well as the benefits provided by the versatility of the pultrusion process,
translates to a wide range of applications across various industry sectors. Where
composite pultruded elements are found, is a function of the FRP’s mechanical
properties, high strength-to-weight ratio, corrosion resistance, and design flexibility.
This chapter provides an overview of where pultruded components are used
across various industry segments, beginning with those that go beyond building
related applications, and then providing relevant state-of-practice examples that
are found across built infrastructure and other related sectors.
The selected projects presented herein focus on recent applications, or highlight other critical projects with key attributes where FRP pultruded components
are used, in lieu of alternative traditional materials (such as wood, steel, and
aluminum). This chapter aims to help industry stakeholders understand from a
practical point of view how FRP pultruded elements can be implemented to current
projects and needs.
4.1 APPLICATIONS & SECTORS OVERVIEW
4.1.1 Non-Civil Infrastructure
Common industry sectors and applications where FRP pultruded elements are
currently implemented (beyond buildings and built infrastructure) include:
i.
Aerospace and Aviation: Pultruded composites are utilized widely in the
aerospace and aviation industry, where this was one of the first industries to
adopt FRP pultruded components for applications that require lightweight
and high strength materials. Pultruded components are used in aircraft
components, including wing spars, stringers, floor beams, and interior
panels, contributing to weight reduction and fuel efficiency.
ii.
Automotive: Pultruded composites are increasingly being used in the automotive industry to replace traditional materials like steel and aluminum.
They are used in components such as chassis structures, body panels,
bumper beams, and interior parts, providing weight reduction, and impact
resistance, the use goes beyond cars and is implemented across all types
of vehicles including the trucking and trailer industry sector. FRP components provide this industry benefits due to the lightweight and high-strength
characteristics, resulting in increased payload capacity, improved fuel efficiency, and resistance to environmental factors.
iii.
Electrical and Electronics: Pultruded composites are employed in the electrical and electronics industry primarily for insulating components, as well
as busbars, cable trays, and antenna supports. They offer electrical insulation, in addition to resistance electromagnetic interference improving the
performance of electronic components and signal transmission, while also
resulting in a lightweight design.
iv.
Sporting, Recreational and Outdoor Equipment: Pultruded composites
are widely used in the manufacturing of sporting goods across multiple
applications such as fishing rods, tennis racquets, golf club shafts, archery
equipment, hockey sticks, skiing and snowboarding equipment like poles
and boards, water sport equipment like paddles, kayaks and boards, and
bicycle frames amongst other examples. Pultruded components provide
high strength, flexibility, and durability while enhancing performance and
reducing weight. Additionally, pultruded elements are extensively implemented in other high-performance sports such as sailing and motor racing,
where the material properties need to be light weight, buoyant, and versatile. Moreover, pultruded elements are typically pushed to the limit of their
performance. These applications offer an outlook on what can be achieved
with FRP pultruded elements.
4. FRP PULTRUDED COMPONENTS: WHERE 37
v.
vi.
Industrial: Pultruded composites find applications in various industrial
sectors for processing equipment and machinery components. They are
used in conveyor systems, grating, ladder and platform systems, chemical
storage tanks, pipe supports, and other industrial structures, offering corrosion resistance, high strength, design flexibility, and abrasion resistance
that outperforms conventional materials in harsh and acidic environments.
Pultrusion is used by many original equipment manufacturer (OEM) products and custom products due to the need for exclusive pultruded parts for
products and systems. Cooling towers are also another industrial application
where FRP pultruded components are used due to the superior design that
delivers cost efficiency via the lowest life-cycle costs. Moreover, thanks to
the versatility of the pultrusion design process, FRP pultruded components
are used in tooling industrial applications, providing ergonomic shapes and
reliability with non-conductive properties.
Other: FRP components used across other sectors such as the mining and
military sectors.
4.1.2 Civil Infrastructure
A summary of sectors and applications where FRP pultruded elements are used
across the different built infrastructure (including buildings) is described below.
Project examples where FRP pultruded components have been used in the built
infrastructure including buildings is provided within this chapter (excluding the
wind industry).
i.
General Construction: Pultruded composites are used in the construction
industry for structural components, such as beams, columns, trusses, and
reinforcement bars. They offer high strength and durability, making them
suitable for bridges, sidewalks, decks, boardwalks, stairs, and other infrastructure projects. FRP pultruded bars, meshes, and dowels used as internal
concrete reinforcement have also seen a significant increased use in the
construction industry. Additionally, FRP pultruded elements are used in
scaffolding systems, as well as cladding systems and components such as
windows, panels, and other fenestration applications.
ii.
Specialized Construction: FRP’s durability makes it a preferred choice
for many specialized construction projects, such as data centers, cooling
towers, and industrial type projects where FRP frame structures are used
to support equipment or piping. FRP is the preferred material due to its
ease of assembly, easy to cut, speed of installation, and minimal maintenance, lowering life cycle costs. In these types of sectors, the critical path
in construction is typically driven by other factors than the structure (e.g.
mechanical and electrical needs).
iii.
Transportation: FRP is increasingly becoming the material of choice in
the mass transit and rail sector due to its lightweight nature, prefabricated structures, rapid installation, corrosion resistance, low maintenance
requirements, and, most importantly, the extended service life of structures
used in railway platforms, decks, coverboards, walkways, guardrails, sound
barriers, signposts, and other transportation infrastructure applications.
iv.
Waterfront: Pultruded composites are widely used in the waterfront infrastructure sectors going beyond coastal applications used in dams, rivers,
locks…etc. as well as maritime and water way industry sectors for applications like decks, sea walls, locks and gates, fender systems, piles and
sheet piles, guide walls, camels, ship separators, docks, and marina structures. Additionally, pultruded composites are utilized in offshore structures,
including oil platforms and subsea components. FRP components offer
resistance to corrosion, moisture, and UV radiation, making them ideal for
such marine environments.
v.
Utility and Telecommunications: This growing sector for FRP pultruded
applications is attributed to the durability, non-conductivity, low-maintenance, and EMI/RFI transparency of pultruded glass and basalt FRP
38
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
vi.
components. FRP components are widely used for items such as utility
cross arms, line markers, electrical lines, wastewater and water treatment
components, non-conductive ladder rails, and fiber optic cabling. Additionally, utility poles are seeing a growth due to fire resistance and improved
performance amongst other reasons.
Wind industry: The wind industry is one of the most advanced sectors in
which FRP pultruded sections have been used and are continued to be used.
The need for lightweight, durable, and versatile materials has positioned
FRP pultruded materials as one of the preferred material solutions for this
sector. FRP components are used where the high strength and stiffness
allows the blades to withstand the loads and stresses encountered during
operation, as well as used in the turbine tower. FRP pultruded components
are also employed in the manufacturing of various nacelle components
such as structural supports, cable trays, covers, and access platforms. These
pultruded profiles offer lightweight and durable solutions that are resistant
to corrosion and fatigue.
4.2 COMMON COMPONENTS
FRP pultruded components have numerous attributes, with one of the most
significant innate qualities being their versatility in manufacturing and designing
components. The common denominator is having a constant cross-section. This
means that the pultruded manufactured components can be fabricated in an infinite number of combinations based on the reinforced fibers, resins, and additives;
which will vary based on the application as previously discussed. Below are the
most common and currently available FRP pultruded components. Refer to Annex
B, which provides a list of Pultex®, readily available FRP pultruded components
and properties by Creative Composites Group. Section 11 of this document also
contains the contact information for FRP composite manufactures.
i.
Structural Shapes: Pultruded profiles can be used to create load-bearing
structural shapes similar to steel structural shapes (I, H, W…etc.), as
presented in Figure 16. These components are used in multiple framing
type structures including mezzanines, custom buildings, pedestrian bridges,
access structures and other applications. Unique cross-sectional shapes can
be created for specific purposes, such as pultruded I-bars, which can be
used to construct strong and corrosion-resistant walking surfaces while flat
beams are an ideal structural component for many construction projects.
ii.
Channels: Pultruded channels are similar to steel ‘C’ sections and are
particularly useful in applications where corrosion is a concern or lightweight structural shapes are required for easy and speed of installation in
comparison to metallic sections, as seen in Figure 17. Channels can be cut
and shaped using simple tools and can be coupled together to make H or I
style sections. Additionally, pultruded channels are commonly used as floor
joists, in pedestrian bridge components as corrosion-resistant safety rails,
crossing arms, and highway sound barriers. Many times, channels are used
to create truss structures.
iii.
Angles: Pultruded angles are like steel ‘L’ sections and like structural
shapes and channels, are ideal for outdoor construction projects due to the
durability attributes, as seen in Figure 18. Angles are found in an array of
applications commonly used as bracing, connections, tension members in
an array of FRP structures.
iv.
Poles and Tubes: FRP pultruded tubes (like rectangular, square and circular
HSS steel sections) are used for handrail and many framing structures as
primary load bearing elements as well as standalone structures such as
piles, poles, light posts, flag whips and flag poles, as seen in Figure 19.
Other applications include electric fence poles, columns, golf flag poles,
high jump poles and cross bars, antennas, etc.
v.
Bars and Rods: Solid FRP pultruded components such as reinforcement
bars (rebars), dowels used for internal reinforcement of concrete or masonry
4. FRP PULTRUDED COMPONENTS: WHERE 39
vi.
vii.
structures, and rods used for in
multiple industrial or system
applications
are
another
common type of shape. FRP
rebars are differentiated from
other pultruded components as
a surface enhancement feature
such as sand costing or helical
wrapping is needed to provide
mechanical bonding between
the FRP bar and concrete, as
seen in Figure 20. They are
Figure 16 – FRP structural shapes
mainly used to replace carbon
steel and avoid corrosion.
Gratings: Pultruded grating
systems with an array of crosssectional shapes and forms
are available and primarily
used as flooring or walkway
surfaces in industrial plants,
Figure 18 – FRP structural angles
offshore and marine strucFigure 17 – FRP structural channels
tures, and commercial buildings, as seen in Figure 21.
They offer a lightweight and
corrosion-resistant alternative
to traditional materials such
as steel grating, that allow
easy access, handling, and
maintenance, while providing
enhanced durability. Gratings
can be manufactured with
surface coatings to provide
slip resistant walking surfaces.
Panels and Sheets: Pultruded
panels and sheets can be
either laminar or have hollow
sections, typically with a
smaller thickness compared
to the surface area they cover.
FRP panels can also be filled
with
insulation
material
Figure 19 – FRP rectangular, square, and circular components
crating ‘sandwich panels’,
especially if used in walls and roofs as seen in Figure 22. Panels and sheets
can be used in combination with structural shapes, as well as in geotechnical application as sheet piles.
4.3 GENERAL CONSTRUCTION
The following Chapter sub-section provides 32 recent civil infrastructure
construction projects from the different sectors previously reviewed. The projects
reveal the implementation of FRP pultruded components in different built infrastructure and building examples (excluding wind industry). A summary list of the
samples is provided in Annex C. For each example, the key aspects driving the
rationale for selecting and using FRP pultruded components over conventional
materials in highlighted.
4.3.1 Structural Framing
Example: FRP profiles at the façade of a building on the University College
Ghent’s Schoonmeersen Campus (Ghent, Belgium). 2012.
40
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Figure 20 – FRP concrete reinforcement bars, dowels, and rods
Figure 21 – FRP gratings
Figure 22 – FRP panels and sheets
Figure 23 – FRP profiles at the façade of a building on the University College
Ghent’s Schoonmeersen Campus (Source: Open Oproep 2113)
The façade of the Soag Building for
Study of Social Work on the University College Ghent’s Schoonmeersen
Campus was built using 120 ft long
FRP structural profiles, as seen in
Figure 23. The building was designed
by Slovenian architects Sadar+Vuga,
specialists in an open, innovative,
and integral architectural design
and urban planning. Their concept
was a new school environment – ‘a
hybrid studyscape’ – where students,
teachers, visitors, and the general
public can meet, interact, study, work
and play. The structure communicates
with its immediate surroundings via a
permeable shading membrane made
up of horizontal composite lamellas
which wrap around the building’s
glass façade.
Glass fiber composite profiles were
chosen for this application for their
ease of installation and ability to meet
the demanding aesthetic requirements
of the project. The design flexibility
with composite materials enabled
the custom shapes envisaged by the
architect to be built.
Example: FRP framing replaces
deteriorated steel framing in trickling
filter (Girardeau, Missouri). 2014.
The City of Cape Girardeau, MO,
turned to fiberglass when it came time
to renovate its wastewater treatment
facility. Years of exposure to chemicals had left a trickling filter at the
city’s wastewater treatment plant the
worse for wear. The chemicals had
eaten away at the metal structural
members and bracing components
inside the trickling filter, and the
corroded parts needed to be replaced
as seen in Figure 24. In addition,
the unsightly building panels on the
outside of the trickling filter were
splitting and needed replacement as
well.
A structure that is 100’ long, 60’
wide and 45’ tall can require a lot of
effort to maintain, especially in such a
corrosive environment. That was a key
consideration for the owner to choose
composite materials over traditional
steel beams. For this project, wide
flange beams, plates and angles were
chosen to replace the corroded metal
4. FRP PULTRUDED COMPONENTS: WHERE 41
structural members in order to extend the service life of the structure and reduce
future maintenance costs.
Example: FRP temporary shelter located inside a deteriorated church (L’Aquila,
Italy). 2010.
One of the largest FRP strut and tie spatial structures ever built is represented
by the 11,300 ft2 by 100 ft high FRP temporary shelter located inside the church
of Santa Maria Paganica in L’Aquila, Italy, in order to protect the monument after
the 2009 earthquake. The frame joints use conventional steel plates and gusset FRP
plates as seen in Figure 25.
The main reason why FRP profiles were used was the lightweight and ease of
installation. Being a historic building, adding additional loads to the structure
would compromise the structural integrity of the existing building. Having a material like FRP that is 25% of the weight of steel, presented an ideal solution for this
project.
Example: Freestanding CFRP roof at the Apple Campus 2 ‘Theatre’ (Cupertino,
California). 2019.
Situated in Cupertino, CA at Apple Park, the Apple Campus 2 structure features
the world’s largest floating carbon fiber roof. Expanding on the work done at the
Chicago flagship store, this subterranean auditorium is more than 120,000-squarefeet and is designed as a theater. With seating for up to 1,000 guests, it also features
a curved glass exterior wall comprised of 900 panels. With a 14-foot diameter, the
floating carbon fiber roof is the largest in the world (see Figure 26). It was built
using 44 identical panels that are 70-feet long and 11-feet wide. The entire floating
roof weighs approximately 80 tons, significantly lighter compared to using steel
or aluminum.
The main reason for the use of FRP in this project was the lightweight nature
of the panels and the flexibility of such composite elements to adapt to complex
architectural designs as the one used in the Apple Campus 2.
4.3.2 Concrete Reinforcement
Example: Secant pile seawall
behind beach dunes to protect SR A1A
(Flagler Beach, Florida). 2019.
The 4920’ long secant pile seawall
of the SR A1A road in Flagler Beach,
Florida, was rebuilt using glass FRP
(GFRP) reinforcement after the catastrophic damages caused by the Hurricane Matthew to the traditional steel
sheet pile seawall (Figure 27).
GFRP reinforcement was chosen
over traditional steel due to its durability, given that the seawall was built
on the coast where the presence of
chlorides would otherwise corrode the
traditional steel reinforcement. This
was the first Florida Department of
Transportation (FDOT) project with
greater than one million linear feet of
GFRP reinforcement, and was finished
ahead of schedule in part due to the
speed of assembling and installing the
pile cages.
Example: Jizan Flood Mitigation
Channel (Jizan Economic City, Saudi
Arabia). 2020.
Jizan is the capital of the Jizan
Region, which lies in the southwest
Figure 24 – FRP framing replaces
deteriorated steel framing in trickling
filter (Source: Strongwell)
Figure 25 – FRP temporary shelter located inside a deteriorated church
Figure 26 – Freestanding CFRP roof at the Apple Campus 2 ‘Theatre’ (Source:
Tencom)
42
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Figure 27 – Secant pile seawall reinforced with GFRP (Source: University of
Miami)
Figure 28 – Jizan Flood Mitigation Channel (Source: IKK Mateenbar)
Figure 29 – BFRP reinforced topping slabs of the Avocet Tower (Source: Mafic
USA)
corner of Saudi Arabia; disastrous
flash flooding occurs during periodic heavy rains due to runoff from
nearby mountains. The 23-kilometerlong reinforced concrete stormwater
drainage channel (see Figure 28) was
built to protect a large industrial zone
that includes oil refinery operations
for Saudi Aramco (Dhahran, Saudi
Arabia).
The high salinity in the region’s
sand and high delta in temperature from day to night causes faster
cracking in concrete structures. GFRP
was used to extend the service life of
the structure and avoid the inevitable
corrosion when using steel reinforcement in such environment. Additionally, due to the lightweight of the
reinforcement, the construction time
was significantly reduced due to the
ability to deploy and install the FRP
reinforcement bars over the large area
of the project, compared to steel.
Example: BFRP reinforced topping
slabs of the Avocet Tower (Bethesda,
Maryland). 2021.
The topping slabs of a 22-story
office and hotel building in Bethesda
(Maryland) were reinforced with
Basalt FRP (BFRP) reinforcement
(Figure 29). The topping slabs had a
surface area of 5,160 sq. ft. and the
thickness varied from 3 to 5 in. To
satisfy the design requirements, the
topping slabs were reinforced using
#3 BFRP rebars placed 12 in. o.c. in
both directions.
Basalt FRP bar reinforcement was
used instead of steel to avoid corrosion due to the frequent use of de-icing
salts in the area during the winter
months. Additionally, this aided to to
expedite the construction process by
using a lightweight material.
Example: Concrete repair of the Negrelli viaduct in Prague using BFRP mesh
(Prague, Check Reepublic). 2017.
Built in 1850, the 1150 m double-track bridge crosses the Vltava River and
continues through the Karlín area of the city, connecting Praha Masarykovo station
with Prague Bubenec station. The renovation project, which began in April 2017,
sought to maintain the viaduct’s existing empire style.
Parts of the viaduct were repaired using externally bonded BFRP mesh (Figure
30). The BFRP mesh used was 2.2 / 50 × 50 - 0.80 x 30m. Thanks to the durability
and enhanced properties of BFRP, material savings were achieved by reducing the
required repair material from 70 mm, which would have been necessary with traditional steel mesh, to just 40 mm when using BFRP mesh. Using BFRP mesh also
resulted in significant time savings due to ease of installation of mesh.
4. FRP PULTRUDED COMPONENTS: WHERE 43
Example: FRP dowels in new
highway Route 219 and Route 33 East
(Elkins, West Virginia). 2002.
FRP dowels were used for new
pavement construction and rehabilitation of damaged pavement sections.
FRP dowel joints were used for new
highway pavement construction
on Route 219 and Route 33 East in
Elkins, WV (Figure 31). Dowel bars
with 1.0- and 1.5-inch diameter were
supported by plastic baskets at design
spacings of 6, 8, 9 and 12 inches.
Plastic baskets were anchored by
either steel stakes or plastic stakes.
In addition to the added durability
by using a non-corrosive shear reinforcement, FRP dowels are frequently
chosen over traditional steel dowels
for their high-performance and ease
of installation due to their lightweight.
Example: BFRP reinforced concrete
retaining wall at the Port of Miami
tunnel (Miami, Florida). 2014.
Basalt rebar (BFRP) was used in the
concrete retaining walls of the Port of
Miami tunnel. Bars of 8 mm and 12
mm diameter basalt rebar with 3”
clear cover was used (see Figure 32).
Wall thickness and shape remained
per conventional design.
Basalt rebar was used in lieu of
steel as a demonstration project to
evaluate performance under service
and environmental conditions, identify and quantify the interface between
BFRP bars and concrete, and evaluate
thermal and physical properties of
BFRP.
Example: Prestressed FRP laminate
system for strengthening the Fenghu
River bridge (Shangai, China). 2015.
During the regular inspection of
Fenghu River Bridge in Fenghuang
Expressway, cracks were found in
many structures. Therefore, under
the actual operation load, the flexural
capacity of box girder was insufficient, so it was decided to reinforce
it using a high-modulus prestressed
carbon fiber reinforced polymer
(CFRP) pultruded laminate system
to improve the original structure,
repair the cracks, improve the bearing
capacity and durability of the bridge
(Figure 33).
The main reason for choosing
CFRP laminates as the repairing mate-
Figure 30 – Repair of the Negrelli viaduct in Prague using BFRP mesh (Source:
Binevir Composites)
Figure 31 – Use of FRP dowels in new highway Route 219 and Route 33 East
(Source: FHWA)
Figure 32 – BFRP reinforced concrete retaining wall at the Port of Miami tunnel
(Source: FDOT)
Figure 33 – Installation of the prestressed FRP laminate system for strengthening
the Fenghu River bridge (Source: Horse Construction)
44
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
rial was the high strength and stiffness of the material. The lightweight nature of
the CFRP laminates also facilitated the repair process.
FRP bars and meshes for concrete reinforcement is a separate sib-segment of
the FRP pultruded composites, due to the combination with concrete requiring
design of the reinforced concrete element (beam, column, slab, joint…etc). While
there have been hundreds of FRP reinforced concrete structures built across North
America and around world, the use of FRP as concrete reinforcement remains
more of a novel application, which is projected to continue growing and increase
(2023 Lucintel). This growth has in part been triggered by the recent publication
of the ACI 440.11-22, Building code Requirements for Structural Concrete Reinforced with Glass Fiber-Reinforced Polymer (GFRP) Bars—Code and Commentary’ (ACI 2022) which will be adopted by reference by the International Building
Code (Myers et al. 2023).
4.3.3 Cladding and Fenestration
Example: Fiberglass windows in a residential condo (Gresham, Oregon). 2017.
The Beranger Condos is a mixed-use complex in downtown Gresham, OR.
The four-story structure contains 24 condominium units and 7,000 square feet of
ground-level retail space. Among the highlights of The Beranger Condos’ design
are the tall windows present in the condo units. While the architect originally
specified fixed aluminum storefront for these openings, the building’s owner had
used aluminum in a previous project and was dissatisfied with their performance.
Fiberglass windows provided the quality, aesthetics, and cost-effectiveness he was
looking for (see Figure 34).
The owner was pleased with their exceptionally durable and energy efficient
qualities. But equally appealing was the fact that the building’s 264 double-hung,
fixed frame and horizontal sliding windows were all glazed in a controlled factory
environment, saving time and money during the window installation process. The
flexibility of the numerous fiberglass window options along with their outstanding
performance, helped make The Beranger Condos a welcome addition to downtown
Gresham.
Example: Opaque composite roof tiles in a warehouse in Port of Salaverry (Salaverry, Peru). 2022.
Opaque composite roof tiles were installed in the roof of a warehouse at the Port
of Salaverry to extend the service life due to the harsh environment to which it was
exposed (Figure 35). The tiles are made from glass fiber-reinforced polyester and
have UV protection film on both sides.
The primary reason for using it in this project was its durability, as the warehouse was situated in a corrosive environment rich in chlorides, such as a seaport.
Also, the lightweight of the material accelerated the installation.
Figure 34 – Fiberglass windows in the
Beranger residential condos (Source:
Building Design + Construction)
Figure 35 – Opaque composite roof
tiles in a warehouse in Port of Salaverry (Source: Planefibra)
4.3.4 Pedestrian Bridges and Boardwalks
Pedestrian bridges and boardwalks are one of the most common applications
for FRP profiles. Most of the time, these structures are found in natural places like
parks, lakes, etc. Even large structures can be moved and assembled easily without
the need for heavy machinery. This allows for installation that doesn’t damage
natural surroundings and also has a low carbon footprint. (CCG).
Example: Pedestrian Bridge at Walker Ranch Park (San Antonio, TX). 2006.
This pedestrian/bicycle bridge is located within the Walker Ranch Park in San
Antonio, Texas. It consists of 6 spans 75’ long and 6’ wide (see Figure 36). It
was designed for a live load of 85 psf. The support trusses, the decking and the
handrails are made of FRP profiles which were shipped unassembled and were
assembled on-site. It was designed for a service life of over 75 years.
FRP was selected primarily due to installation and accessibility restrictions,
while ensuring minimal impact to the natural surroundings by the construction
process, reducing the size of geotechnical and foundation work. Installation was
facilitated due to the lightweight nature of the FRP components. Lastly, the dura-
4. FRP PULTRUDED COMPONENTS: WHERE 45
bility offered by FRP in the harsh environment makes the deployment easier and
avoids the maintenance work afterwards.
Example: Pedestrian Bridge, Bermuda Railway (Bermuda). 2021.
This is the world’s longest span FRP pedestrian bridge, composed of 152-ft long
and 8-ft wide spans, as seen in Figure 37. This unique project faced several design
facets ranging from environmental constraints, design criteria, bridge testing,
assembly, and shipping. The bridge utilized the existing railway, and validation
testing of member capacity including truss tension, compression, Euler Buckling
of compression members and connection bearing was conducted. The dead load of
the structure is approximately 65,000 lbs, significantly lighter than concrete and
steel bridges.
FRP was selected for its corrosion resistance and its ability to withstand hurricane-force winds in order to meet local safety and performance codes (Bermuda
Building Code (2015 IBC) and ASCE 7-10, based on allowable stress design
(ASD) method. Hurricane Wind load was based on 158 mph wind (3 second gust)
which results in 67 pounds per square foot net design pressure as if enclosed structure live load, reduced to 65 psf as permitted by IBC. Also, lightweight characteristic of FRP was a critical benefit, due to the limited lifting crane capacity available
in Bermuda for installation of the bridge; where, as part of the test program, the lift
was simulated to ensure an effective construction installation process.
Example: West Hanover Boardwalk (West Hanover, PA). 2007.
The Chattahoochee River Boardwalk has an 80’ span and a width of 6’, divided
in 4 sections (see Figure 38). FRP profiles were used for the support beams, the
deck, and the curb. It was designed for a live load of 85psf, and it was shipped
unassembled.
FRP was chosen instead of wood or concrete as in other areas of the park for
extended durability purposes.
Figure 36 – Composite pedestrian Bridge at Walker Ranch Park (Source: Creative Composites Group)
Figure 37 – Composite pedestrian bridge in Bermuda (Source: Creative Composites Group)
46
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
4.3.5 Vehicular Bridge Decks
Many of the vehicular bridges that use FRP decks are restoration projects that
need a solution for the superstructure that has high capacity but at the same time
is lightweight so that the restored main structure doesn’t need to hold too much
structural dead load.
Example: Blackfriars Bridge (London, Ontario). 2018.
At 143 years old, Blackfriars Bridge in London, Ontario is a rare example of
wrought iron bowstring arch-truss architecture (see Figure 39). It is Ontario’s
oldest working crossing and at 221 ft., North America’s longest working span of
its kind. After four years of closure, extensive restoration work began in November
2017. The truss was lifted from its granite abutments, cut at mid-span, and transported for full rehabilitation. The FRP deck weighs only 25 psf and has curbs with
stainless steel armor for snow plowing. The bridge now carries vehicles, cyclists,
and pedestrians across the Thames River. The FRP deck was key to regaining
structural capability while retaining Blackfriars’ beauty and giving it long-lasting
performance.
Example: Golf Resort Bascule Bridge (Cayman Islands). 2020.
A prestigious golf resort in the Cayman Islands needed a dual-purpose bridge
at their facility to support golf cart traffic and allow watercraft to pass below.
The bridge had to fit accordingly with the resort’s strict design standards yet be
robust enough to withstand the environmental conditions of the Cayman Islands
for decades of maintenance free service. Measuring 38’ in length, the 10’ wide
bridge is able to raise almost 90 degrees to accommodate most water vessels either
via remote or keypad stanchions (see Figure 40). When serving as a bridge, the
structure can support up to 5,000 lbs. One of the design challenges of this particular project was finding the right balance between industrial structural design and
aesthetic appearance.
Figure 38 – Composite boardwalk at Chattahoochee River (Source: Creative Composites Group)
Figure 39 – Installation of the FRP composite deck of the Blackfriars Bridge (Source: Creative Composites Group)
4. FRP PULTRUDED COMPONENTS: WHERE 47
Example: FRP bridge decking at the Franklin Street bascule bridge (Michigan
City, Indiana). 2019.
In February 2019, record-breaking temperatures buckled Michigan City, Indiana’s Franklin Street Bridge. The 87-year-old structure — the lakeshore town’s
only movable [bascule] bridge — crosses Trail Creek, a gateway to Lake Michigan
for locals and tourists (see Figure 41). The structure uses counterweights to raise
and lower its spans to provide clearance for boat traffic. Due to the buckling, the
concrete crumbled, and the bridge needed to be fixed quickly. The repair was done
using FRP decking.
The traditional approach called for a temporary steel plate until the weather
warmed up enough to accommodate the 28-day cure requirement for concrete,
which would have taken months. It also meant paying for two repairs and closing
the bridge to traffic twice. The need for something lightweight eliminated most
material options. But the accelerated construction value of our prefabricated FRP
panels sealed the decision.
4.4 INDUSTRIAL PLANTS
Example: GFRP components for the magnet support structure of the International Thermonuclear Experimental Reactor (Saint-Paul-lez-Durance, France).
Under Construction.
The €18 billion ITER under construction in Saint-Paul-lez-Durance, France, is
designed to demonstrate that fusion power can be produced on a commercial scale,
providing a safe, environmentally sustainable energy source. The ITER will use
hydrogen fusion, controlled by superconducting magnets, to produce massive heat
Figure 40 – Golf Resort Bascule Bridge (Source: Strongwell)
Figure 41 – FRP bridge decking at the Franklin Street bascule bridge (Source: Creative Composites Group)
48
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
energy. In the commercial machines that will follow, this heat will drive turbines
to produce electricity.
The composite pre-compression rings are the cornerstone of the ITER’s magnet
system support structure. They will ensure the operation of the toroidal field coils
employed to create a magnetic ‘cage’ to confine the super-hot (150 million °C)
plasma. To reduce fatigue and deformation of the coils resulting from the powerful
magnetic fields, three pre-compression rings will be placed on top of them and three
below. An extra set of three will be manufactured in case replacement becomes
necessary in future. The pre-compression rings are required to withstand maximum
hoop stresses of up to 500 MPa at room temperature. Glass fibre epoxy composite
with a high fibre content was selected as the most suitable material to withstand
such extreme loads, avoid circulation of electromagnetic currents, and deliver a
long service life. The composite rings will have a diameter of approximately 5 m,
a cross-section of nearly 30 cm x 30 cm and will weigh slightly more than 3 tons
(see Figure 42).
4.5 TRANSPORTATION
4.5.1 FRP for platform structures
The use of FRP for platform structures for transportation applications is increasingly growing. FRP platforms are used for bus stations, train/metro stations,
carpooling stations, etc. Train/metro stations are one of the main applications for
FRP platforms because in addition to benefiting from the durability and ease of
installation that FRP offers, they also benefit from the non-conductivity of FRP
which is a great security benefit in a mode of transport powered by electricity.
Below is a case study of a railroad station.
Example: 45th and Courthouse Square MTA (Queens, NY). 2012.
The deteriorated concrete elevated mass transit platform was structurally failing
and spalling because of deicing salts being applied to the steel/concrete structure
for an extended period of time. The mass transit agency elected to install an FRP
platform deck over existing and retrofitted steel beams. The pultruded deck sections
were prefabricated with the tactile and accommodations for connections and rub rails
and were delivered to the site ready for installation onto the elevated platform (see
Figure 43). The project consisted of two runs of approximately 600’ of platform
requiring 280 prefabricated pultruded panel modules measuring 4’ wide by 12’ long.
Pultruded deck panels were chosen for their speed of installation, corrosion resistance, and lightweight attributes. The work was performed on the weekend and the
panels were placed into position by hand with minimal construction equipment.
4.5.2 Posts and fences
Example: Frangible airport fence at Zilina airport (Zilina, Slovakia). 2009.
Designed to absorb impact and collapse safely, the frangible masts and poles
are used in airports around the world. These fiberglass solutions are manufactured
Figure 42 – GFRP components for the magnet support structure of the International Thermonuclear Experimental Reactor
(Source: Iter organization)
4. FRP PULTRUDED COMPONENTS: WHERE 49
using pultrusion and pull-winding technology for light weight yet rigid solutions
helping to keep airfields safe (see Figure 44).
Fiberglass composites were chosen for this application because they are durable
but at the same time suitable for an emergency event of ‘windowing’, in which an
airplane collides with the fence.
Example: Composite fencing for a pacific coastal resort (Pismo Beach, California). 2017.
In one of California’s premier resorts, Martin Resorts, three miles of metallic
architectural fencing had to be replaced due to the damaging effects from exposure
to ultraviolet light, saltwater spray and winds from the Pacific Ocean (see Figure
45). Within eight years, the original metallic fencing had oxidized, becoming an
eyesore for guests and a concern for maintenance personnel. Due to the nature of
metallic fences, corrosion/rust can quickly create safety concerns. In total, 1,300
linear feet of fence were replaced in this first phase, and it is planned that +14,000
linear feet will be replaced with FRP in the near future.
In addition to corrosion resistance, the lightweight nature of FRP yielded an
estimated 30-50% cost savings on labor and additional equipment required if the
project had used carbon steel. Most of the contributing factors for these savings
were attributed to the heavy weight of transporting, rigging, and fabricating with
steel.
4.6 WATERFRONT
Due to its many advantages, composites are becoming the top contender to
replace aging wood, concrete and metal for marine infrastructure. FRP products
combine high environmental durability with design flexibility. Some of the marine
applications are summarized below. For each application a real project example is
included.
4.6.1 Fender Systems
Fender systems are engineered to protect waterway infrastructure, such as
bridge piers and electric towers, by absorbing impact from barges, ships, and other
Figure 43 – Composite platform deck at 45th and Courthouse Square Queens, NY (Source: Creative Composites Group)
Figure 44 – Frangible fiberglass
airport fence at Zilina airport
(Source: Exel Composites)
Figure 45 – Composite fencing for a pacific coastal resort (Source: Strongwell)
50
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
waterway vessels. The fender components that can be made from FRP include pipe
piles, walers, and dolphins.
Example: Ravenswood bridge fender system (Dania, Florida). 2017.
In 2017, the Florida Department of Transportation rebuilt the Ravenswood
bridge and installed a new FRP fender system to protect the foundations from
vessel impact. The project included 12” and 16” FRP pultruded piles made with
E-glass reinforcement and polyurethane resin. The project required spliced piles,
in some locations, due to overhead height restrictions caused by an existing electrical distribution line that could not be relocated during construction. Field splices
were performed with the aid of FRP splice sections and structural adhesives (see
Figure 46).
FRP was the selected solution for its superior energy absorption and corrosion
resistance compared to other materials.
Example: Wastewater Baffle and Diffuser Walls (California). 2015.
A water district system in California underwent a refurbishment process at its
wastewater treatment facility to better serve its more than 17,000 service connections. A main component of this refurbishment process included the installation of
FRP pultruded baffle and diffuser walls to aid in the processing of increasing water
treatment volumes (see Figure 47). With high exposures to chemical and organic
matter, baffle panels are primarily used to aid in the coagulation and flocculation
processes in primary water and wastewater treatment. Prior to fiberglass, water
flow controls were designed with legacy materials such as concrete, steel, or wood.
Since the introduction and adoption of fiberglass, operators have turned to composites as a way of increasing water processing volumes and combating material
replacement issues related to rot or corrosion. By reducing material replacement
cycles, operators can lengthen the lifecycles of treatment facilities.
Figure 46 – Composite fender system at Ravenswood Bridge in Florida (Source: Creative Composites Group)
Figure 47 – Wastewater baffle and diffuser walls in California (Source: Strongwell)
4. FRP PULTRUDED COMPONENTS: WHERE 51
4.6.2 Sheet Pile Walls
FRP sheet pile walls have been used for over two decades due to the high durability when in contact with seawater. These types of structures are used for waterfront protection, erosion control, landscaping and more.
Example: Laurence Harbor Wastewater Facility Storm Surge Protection wall
(New Jersey).
The Old Bridge Municipal Utilities Authority, located on Raritan Bay needed to
protect the Laurence Harbor Wastewater Facility from future storm surge. GFRP
sheet pile was selected to help accomplish this task (see Figure 48). The project
included driving 2 separate sheet pile walls as part of the 700 linear foot retaining
wall and 650 linear foot anchor wall. The structure was later backfilled, a concrete
walkway was poured on top and rip rap stone placed in front along the shoreline.
An additional 765 linear foot flood control wall was driven closer to the facility as
a second line of defense and then capped using FRP channels.
FRP materials were selected over traditional materials due to the necessity for
a lightweight solution (easier installation) and the durability requirements for this
project.
Example: United States Navy Pier (Chollas Creek, San Diego, CA). 2005.
Approximately 1,200 lineal feet of seawall using FRP sheet piles, walers tie rods
and nuts were installed with water jet and vibratory equipment (see Figure 49).
The fiberglass sheet pile and walers, injection ports, and plastic lumber spacers
were pre-assembled in panel sections on land and were lifted by aerial crane for
assembly in front of a deteriorated concrete seawall. Upon assembly (interlocking
the panels) and attachment of fiberglass threaded rod/nut into concrete wall/fiberglass sheet pile and waler, grout was injected into the port holes from the bottom
upwards in lifts.
Soil conditions were medium dense sand. Exposure of the wall varied. Sheet
lengths between five and 22 feet were used. A complete fiberglass composite sheet
pile, waler, and tie rod were used for long term performance. Other seawall products were rejected due to poor long-term performance and durability.
4.6.3 Dock and Marinas
Different FRP components and shapes are used to build fully non-corrosive
docks, marinas, and harbors. Compared to traditional materials, FRP profiles offer
fast-construction methods and long-lasting solutions. Also, in the case of a pier
which will require concrete fill, there is no need for formwork as the pilings, caps,
and beams all function as a stay in place form.
Example: Residential composite pier (Bath, ME). 2010.
Figure 50 shows the pictures of one of many residential piers upgraded by
sleeving old timber pilings with FRP composite material for protection against
degradation.
Figure 48 – Laurence Harbor Wastewater Facility Storm Surge Protection wall
52
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Figure 49 – Composite sheet piles at
the United States Navy Pier (Source:
Creative Composites Group)
Figure 50 – Residential composite pier (Source: Creative Composites Group)
4.6.4 Offshore Structures
Offshore structures are constantly subjected to corrosive environments with
high levels of chlorides, humidity, and other agents that induce the deterioration of
traditional materials such as steel, reinforced concrete, or wood. The use of FRP
has gained a lot of attention for these types of applications. Below is an example
of an offshore oil platform.
Example: Offshore oil platforms using FRP grating (California). 1979-2020.
In 1979, over 10,000 square feet of pultruded grating was installed in lieu of
steel grating in the well bays and adjacent areas on Shell’s offshore platform Ellen
(see Figure 51). The platform was destined for the Beta Field off the shore of
southern California. Now, with over 40 years of use, the grating continues to show
an excellent return on investment for current operators, Beta Offshore. When asked
in 2010 about the lifespan of the grating on the platform, the Facility Superintendent at that time stated, “The grating looks to be in great shape. The surface shows
very little wear and tear.”
In 2020, Strongwell was able to acquire and examine a portion of the original
grating for flexural testing. The removed panels were taken from an area on the
offshore rig that received heavy daily foot traffic and constant UV exposure. Upon
visual inspection, the grating had some cosmetic wear with no visual signs of glass
exposure. With over 40 years of daily exposure to weather and pedestrian traffic,
the grating still retained over 80% of its flexural modulus and 80% of its maximum
load capability from its published load tables. As tested against the published data
for that particular series of grating, the extracted sample maxed out at 3,385 lbs.
4.7 UTILITY AND TELECOMUNICATIONS
4.7.1 Utility Poles
FRP profiles are used in various utility infrastructure applications, such as utility
poles, light poles and crossarms. Compared to those made from traditional materials (e.g.. wood, steel, concrete), they offer better resiliency and easier maintenance, both of which make for a superior long-term investment. Find below a case
study for utility poles.
Example: Self-Extinguishing Utility Poles (California, USA).
California is considered the epicenter of fire events. Chaparral covers more than
14,000 square miles of the Golden State (see Figure 52). When a standard wood
utility pole is exposed to fire, it loses strength and must be replaced. Some of the
FRP poles in the market don’t have to be replaced if the temperature is below 400
ºF, maintaining grid reliability and uptime.
Multiple utilities in California are switching their wooden poles to FRP (as seen
in the pictures below) to provide additional fire hardening and grid enhancement
for their unique environment.
4.7.2 Cross-Arms
Example: Fiberglass cross-arms for substation (Johnson City, Tennessee). 2018.
The municipal power provider is using 34’ long rectangular cross-arms at a
substation that generates electricity for the Johnson City Water Works’ Watauga
4. FRP PULTRUDED COMPONENTS: WHERE 53
Figure 51 – Offshore oil platforms using FRP grating (Source: Strongwell)
Figure 52 – Composite water clarifier tank covers (Source: Creative Composites Group)
River Plant (see Figure 53). The tubing replaces wooden cross-arms that supported
electric wires that feed power to a group of transformers at the substation. The
department began searching for alternatives after having to replace the wooden
cross-arms that were supposed to last for 30 years after only ten years of use.
Fiberglass tubing was chosen over steel because of its non-conductive quality in
addition to being lightweight, more durable, and quicker and easier to install than
steel or wood.
54
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
4.7.3 FRP Panels
Example: Structural insulated panels for refrigerated facility for Hidewood
Meats (Brandt, Minnesota). 2022.
Hidewood Meats provides custom meat processing of beef, pork, lamb, goat,
and deer. It is also a retail outlet for meat, seasonings, sauces, cheese, and honey.
The owners chose FRP structural insulated panels (SIP) for all the exterior walls,
most of the interior walls, and the roof over all of the cooled spaces, mainly due to
the high insulation properties (see Figure 54).
The most important factor in thermal efficiency is the continuity of the insulation. The SIP system provides a solid envelope of continuous insulation. These
panels have the ability to resist heat transfer by both conduction and convection.
By comparison, according to an Oak Ridge National Laboratory study, a conventional stick-built wall would require an R-value of R-40 to compete with a 6-inch
SIP wall (R-24). Using SIPs with factory installed Fiberglass reinforced plastic
(FRP) also saved a huge amount of on-site labor cost. FRP panels were installed
for all interior surfaces; because it is a food processing facility, stainless steel nails
were used to connect the SIP panels.
4.7.4 Industrial Tanks & Processing Equipment
Corrosion is a serious challenge for industries that use water and chemicals. Fiber
reinforced polymers (FRP) have the durability and abrasion resistance to outperform conventional materials under these conditions. FRP is often used for piping,
tanks, scrubbers, custom equipment, and many other vessels.
Below, two case studies are presented in which FRP was used for industrial
applications.
Example: University of Arizona Cooling Tower (Tucson, Arizona). 2008.
This 36’ by 36’ four-cell cooling tower combines custom fiberglass components
and structural shapes (see Figure 55). Pultruded pieces meant less time and money
for construction.
The pieces are chemically resistant, low-maintenance, and were manufactured in
a custom color to complement the campus architecture.
Example: Water Clarifier Tank Covers (Kelowna, British Columbia, Canada).
2000.
At this wastewater treatment plant, tank covers had to withstand sub-zero
temperatures and heavy snow. Lightweight and non-corrosive FRP profiles were
used for the 52-foot-long pultruded beams and 25-foot-long flat sheet panels (see
Figure 56).
Installation on the existing concrete fermentation tank took place in freezing
temperatures. Because of its lightweight properties, the installation of the FRP
components were quick and easy compared to conventional materials. Thus, the
work did not require an extensive crew or costly equipment to complete.
Example: FRP profiles in balconies (Pittsburgh, PA). 2016.
Figure 53 – Fiberglass cross-arms for
The Yards at 3 Crossings, a 300-unit luxury apartment building opened its first
substation (Source:Strongwell)
wing in the Spring of 2016. Each apartment has an outside balcony that is trimmed
with large horizontal channels to
create a visual underscore. Architects
originally specified steel channel to
trim the base of each balcony. The
construction company of the project
recognized that the large size and
weight of the steel channel served no
structural purpose. The weight would
add complexity and labor time to the
installation and require additional
equipment. Additionally, the steel
would require future maintenance to
prevent unsightly corrosion on the exteFigure 54 – Structural insulated panels for refrigerated facility for Hidewood
Meats (Source: Enercept)
4. FRP PULTRUDED COMPONENTS: WHERE 55
rior of this upscale development (see
Figure 57).
Finally, pultruded 18” x 2-1/2” x
1/4” FRP channels were selected as
the best solution for the project. These
channels weigh significantly less
than the steel channels. The channels
were custom manufactured, cut each
channel to length and predrilled all
mounting holes so that the channels
were ready for installation at delivery.
Before installation each channel was
coated with aliphatic polyurethane to
protect from UV exposure.
Figure 55 – Fiberglass components at the University of Arizona cooling tower
(Source: Creative Composites Group)
Figure 56 – Composite water clarifier tank covers (Source: Creative Composites
Group)
Figure 57 – FRP profiles in balconies (Source: Creative Composites Group)
56
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
5. FRP PULTRUDED COMPONENTS: WHY
FRP pultruded materials are an enabling solution for built infrastructure applications. FRP pultruded elements are enabling by providing an opportunity to rethink
and reshape how to design our built infrastructure, based on the key attributes of
FRP composites. The widespread use of FRP pultruded components in our built
infrastructure is reaching a critical moment. Understanding why pultruded components need to be used in the different built infrastructure applications, will result in
its further implementation.
5.1 FRP KEY ATTRIBUTES
FRP pultruded components have many beneficial qualities that make it a suitable
alternative to more traditional construction materials such as wood, steel, concrete,
or aluminum. FRP pultruded components offer several advantages specifically
when applied to built infrastructure applications, for the following reasons:
i.
ii.
iii.
iv.
v.
vi.
vii.
Corrosion Resistance: FRP pultruded components are non-metallic, hence
inherently corrosion resistant. Unlike traditional metallic elements, it does
not rust or corrode when exposed to harsh environmental conditions, chemicals, or moisture. This key property is one of the initial driving benefits,
making FRP ideal for infrastructure in innate corrosive environments, such
as coastal areas or chemical processing plants, extending the service life of
the built infrastructure.
Durability and Longevity: FRP pultruded components have excellent durability and long service life. They are resistant to UV radiation, moisture,
and chemicals, making them suitable for outdoor applications. Their structural properties remain stable over time; hence this minimizes the maintenance requirements and offers long-term cost savings over the service
life of infrastructure. Longevity in direct UV exposure will depend heavily
on the resin formulation, light absorber additives, color, fiber architecture
and if the profile has been coated with an advanced UV coating such an
aliphatic polyurethane or fluoropolymer UV protective layer.
Lightweight: FRP pultruded components are lightweight compared to their
metallic counterparts. This characteristic simplifies transportation, installation, and handling processes. Lighter elements also reduce the overall
structural weight, which can lead to cost savings, easier construction, and
improved performance, as exemplified in seismic areas.
High Strength-to-Weight Ratio: FRP pultruded components offer an excellent strength-to-weight ratio. FRPs have high tensile and flexural strength
while remaining lightweight. This feature enables the efficient and optimized design of structural systems, reducing the amount of material needed
and providing cost-effective solutions.
Design Flexibility: FRP pultruded components can be customized and
manufactured in various shapes, sizes, and configurations when assembled.
This flexibility in design allows for tailored solutions to meet specific
project requirements. FRPs can be easily fabricated into complex shapes,
even curved profiles, and intricate cross-sectional geometries, enabling
architects and engineers to explore innovative designs.
Electrical and Thermal Insulation: FRP pultruded components provide
electrical and thermal insulation properties. FRPs do not conduct electricity, making it suitable for applications where electrical insulation is
required. Additionally, FRPs have low thermal conductivity, reducing heat
transfer and providing insulation benefits in buildings and infrastructure,
especially when looking at connection of elements.
Non-Magnetic: FRP pultruded components are non-magnetic, which is
advantageous in environments sensitive to magnetic fields. This property
makes FRPs suitable for applications where electromagnetic interference
(EMI) must be minimized, such as in healthcare facilities, data centers, toll
5. FRP PULTRUDED COMPONENTS: WHY 57
plazas, metro lines, electrical sub-stations, or structures where telecommunication interference needs to be reduced.
vii.
Sustainable: FRP pultruded components are environmentally compatible
and sustainable. Due to its lightweight nature, it contributes to reduced
transportation energy requirements. Its long service life reduces the need
for frequent replacements, thus reducing material consumption and waste.
Moreover, the manufacturing of pultrusion is an efficient process that
increases productivity and reduces waste during production. Although not
commonly performed, pultruded products can be recycled. The matrix is
separated from the glass and the glass is repurposed back into the production cycle of composites while the matrix is used to generate heat.
Overall, FRP pultruded elements offer a range of advantages, including corrosion resistance, lightweight construction, high strength-to-weight ratio, design
flexibility, durability, and sustainability. These attributes make them valuable for
various infrastructure applications, such as bridges, buildings, utility structures,
marine structures, and rehabilitation projects. FRPs are also thermally and electrically non-conductive, making them a great insulator. In the following sections, the
key attributes are highlighted and evaluated where FRP pultruded components are
used across the different the built infrastructure, including buildings.
5.2 GENERAL CONSTRUCTION
5.2.1 Structural Framing
• Lightweight Construction: The low weight of FRP pultruded structural
elements provides a significant advantage in terms of erection speed and the
construction process, enabling easy, rapid, and cost-effective installation.
Furthermore, the lightweight nature of FRP elements facilitates the construction of structural frames in remote or difficult to access locations, as well as
in areas with limited mechanical capabilities, such as low-capacity cranes.
This capability enables structural frame construction that would otherwise be
impossible or cost prohibitive.
•
Thermal Properties: Due to the thermal insulation properties, FRP components
do not cause ‘cold bridges’, hence improving the overall thermal properties of
structural frames by isolating potential thermal bridges.
5.2.2 Concrete Reinforcement
• Corrosion Resistant: FRP is corrosion resistant, which translates to more
durable concrete structures. No corrosion means no cracking, spalling and
no need for maintenance related to corrosion caused preventative or reactive
damage.
• Lightweight Construction: The low weight of FRP reinforcing bars and other
concrete reinforcement products provides a substantial advantage which
results in easy, rapid, and affordable rebar placement (less labor needed). It
also allows for concrete reinforcing materials to be transported at a lower cost
as a single truck load can transport four times as much material.
• Concrete: When concrete structures use nonmetallic reinforcement, the
concrete mix and design of concrete structural elements result in significant
benefits such as i) concrete cover can be reduced, resulting in less concrete
usage; ii) contaminated or recycled concrete aggregate is feasible, reusing
materials that otherwise would end up in a landfill; iii) saltwater can be used
in the concrete mix, allowing to save fresh water a scarce resource; iv) chloride limits applied to cement and concrete can be disregarded, since there is
no metal in the concrete and thus no corrosion; and v) admixtures used to
passivate steel or improve the ‘corrosion resistant’ properties of the concrete
can also be disregarded in the mix, further reducing the cost of concrete.
58
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
5.2.3 Cladding and Fenestration
• Corrosion Resistant: FRP is corrosion resistant, which translates to more
durable skin elements that resist an array of varying weather conditions,
making FRP cladding and fenestration an adaptable and versatile ‘skin’ system
for buildings and structures.
• Lightweight Construction: The lightweight nature of FRP pultruded structural elements provides a significant advantage in terms of erection speed,
the construction process, enabling easy, rapid, and cost-effective installation.
• Design: FRP can be engineered with ideal structural properties and complex
cross-sectiosn to match any design requirement, resulting in customizable
cladding and fenestration parts and elements.
• Thermal Properties: Due to the thermal insulation properties, FRP components do not cause ‘cold bridges’ hence being able to use as components to
isolate cladding elements, as well as improving the overall thermal properties
of cladding and fenestration solutions.
5.2.4 Pedestrian Bridges and Boardwalks
FRP structures and decks for pedestrian bridges offer multiple benefits, including:
• Lightweight Construction: An FRP deck weighs 80% less than that of a
comparable reinforced concrete deck. This is a significant reduction in deadweight to the super structure and foundations. In addition to reducing strain on
the bridge’s structure, this weight reduction is also a substantial advantage in
the construction process, allowing for easy, rapid, and affordable installation.
• Corrosion Resistant: FRP surfaces resist degradation from all common corrosive and abrasive influences. Even power-washers or petroleum-based chemicals won’t damage the surface, not to mention the material’s inherent UV and
weather resistance.
• Maintenance: Steel reinforced concrete bridges have a standard life span of
15-20 years, especially when exposed to chemicals or harsh weather. Because
FRP withstands degradation from those same forces, it has a substantially
longer working life, with an expected service life of an FRP deck of 75
years with no maintenance, even when installed in aggressive environmental
conditions.
• Cost Effective: The use of FRP enables eliminating significant level of maintenance of these types of structures, which comes with a financial incentive.
Choosing a durable material that requires limited or no maintenance service
saves a substantial amount throughout the life of the structure, considering
both the cost of materials as well as labor costs; where the latter is increasing
at a higher rate with the limited availability of skilled labor.
• Design Flexibility: FRP can be engineered with ideal structural properties to
match almost any load. FRP can also be fabricated in customizable panels,
which allows easy installation regardless of bridge shape or size.
5.2.5 Vehicular Bridge Decks
The main advantages of vehicular FRP bridge decks are:
• Lightweight Construction: FRP’s weight reduction reduces strain and stresses
applied on the bridge’s structure, which means that the existing foundations
may be used as is without further work. Lightweight also makes installation
easy, fast, and affordable, while the quick installation minimizes traffic delays,
reducing the cost associated with that. The use of lightweight decks allows
many existing bridge structures to maintain their posted capacity due to the
significant deadload reduction when compared to concrete. This is of special
interest to owners and maintainers of historic bridges.
• Design Flexibility: FRP can be engineered with ideal structural properties
to handle an array of load conditions. FRP decks are made of customizable
panels, which makes easy installation possible regardless of a bridge’s shape
or size. At weights less than 26 pounds per square foot, the FRP deck is a good
solution for movable bridges due to the high strength-to-weight ratio.
5. FRP PULTRUDED COMPONENTS: WHY 59
•
•
•
•
Surface: The polymer aggregate overlays that most of the FRP decks have
been non-slip and can withstand snowplows and are customizable (many
colors, etc.), hence FRPs are well-suited to nearly any type of traffic surface
need.
Corrosion Resistant: FRP surfaces resist degradation from all common corrosive and abrasive influences including deicing chemicals and UV exposure.
Additionally, a solid FRP deck can protect superstructures and mechanisms
from chemicals and other environmental exposure.
Maintenance: Because FRP is corrosion resistant, the material has a substantially longer working life than traditional material such as timber/wood and
concrete decking. FRP decks can last at least 75 to 100 years with minimal or
free maintenance.
Life Cycle Cost Savings: The ability to virtually eliminate or substantially
reduce maintenance also comes with a financial incentive, due to the labor and
material cost savings.
5.3 SPECIALIZED CONSTRUCTION
5.3.1 Data Centers
• Speed of Construction: The lightweight nature of FRP enables easier transportation, handling, and, most importantly, installation of structural components,
reducing construction time and costs. In datacenters, the critical path is typically determined by other project needs, not the structure.
• Thermal properties: FRP components exhibit good thermal insulation properties, which can be beneficial in data centers, helping to maintain stable
temperature and humidity levels within the facility. Thus, reducing the need
for excessive cooling or heating and contributing to energy efficiency.
• Magnetic and Electrical Insulation: FRP components are non-magnetic and
electrically non-conductive, providing insulation properties. In a data center
environment where sensitive electronic equipment is housed, using FRP can
help reduce the risk of electrical shorts, grounding issues, and electromagnetic
interference.
5.3.2 Industrial & Specialized Buildings
• Speed of construction: Similar to data centers, the lightweight nature of FRP
allows for easier transportation, handling, and quick installation of structural
components, as minimizing impact on industrial operations is crucial in the
critical path of construction.
• Corrosion-Resistant: FRP surfaces resist degradation from all common corrosive and abrasive influences including deicing chemicals and UV exposure.
Additionally, a solid FRP deck can protect superstructures and mechanisms
from chemicals and other environmental exposure.
• Design Flexibility: FRP pultruded elements offer greater design flexibility
and customization compared to many traditional materials. FRP can be engineered to have specific properties, since the manufacturing process and material selection can be tailored to meet specific project requirements. This means
that the design of larger clear spans, or unique building needs can be achieved
with FRP pultruded elements.
5.4 TRANSPORTATION
The use of FRP is increasing across multiple transportation sectors such as rail
systems and transit infrastructure. The main advantages of the use of FRP pultruded
components for this type of applications are:
• Durable: Many of the platforms for transportation applications are located
outdoors and are exposed to weather and an array of harsh effects. FRP is
non-corrosive, extending the service life of structures that have often already
exceeded their expected lifespan.
60
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
•
•
•
•
Lightweight: FRP weighs one fourth as much as steel, making the installation of these platforms easier and faster. This is especially important for these
applications since stations must be closed to traffic until the platforms are
replaced.
Electrical Insulation: FRP components are electrically non-conductive and do
not transmit electrical currents. This is crucial especially for railroad platforms
given that most of the trains are electric, platforms are thus electrically insulated from these currents, increasing passenger safety.
High strength: FRP is stronger than many traditional materials like steel,
offering a more efficient solution for transportation applications when considering replacement options for existing structures.
Design Flexibility: Applications for FRP in transportation include platform structures, access structures, stair and railing systems, trackside safety
surfaces, and overhead pedestrian walkways and bridges. Each of which has
different geometrical requirements and complex in-situ accessibility needs.
FRP can be engineered to have specific properties, tailored to meet specific
project requirements. Larger assemblies can be prefabricated and delivered to
the job site for speed of installation.
5.5 WATERFRONT
There are numerous advantages for the use of FRP in waterfront and marine
based applications, which include:
• Strength to Weight: FRP composite structures have a high strength-to-weight
ratio. The high strength and moderate attributes enable FRP profile to absorb
more impact/strain energy than many traditional materials of construction.
• Durability: Since the FRP can be provided with an array of coatings and
finishes, as well as resin formulations the component can be made resistant
to chemical, ultraviolet radiation, range of temperatures, and many of the
environmental hazards found at the waterfront applications, which translates
to extended service life of waterfront and marine structures as FRPs have
minimal documented and accounted for during the design process strength
loss due to fresh and seawater exposure.
• Maintenance: Due to the durability of FRP composites, the expected 75-year
service life can be achieved with little to no maintenance, which can lead to
significant savings over the course of the structure’s life.
• Cost Efficient: FRP composites offer high strength at a low cost, which makes
them a structurally sound and cost-effective material option where high
strength requirements are needed.
• Lightweight: During inspections or other regular maintenance of marine structures, handing, lifting or replacement FRP components is facilitated due to the
lightweight nature of the material.
• Design Flexibility: Applications for FRP waterfront or marine applications
can vary greatly. Each project has different requirements and complex accessibility needs. FRP can be engineered to have specific properties and tailored
to meet specific project requirements.
• Non-Sparking: The non-sparking nature of FRP composites avoids sparks
generation, which should be prevented in certain offshore applications due to
the flammability of the related products.
5.6 UTILITY AND TELECOMUNICATIONS
The main advantages for the use of FRP pultruded components in utility and
telecommunication-based applications are:
• Durability: Corrosion resistance to most chemicals: In many of the industrial processes, multiple chemicals are used (acids, alkalis, salts, oils, strong
oxidizers, and solvents). FRPs can be specifically formulated and manufactured to provide corrosion resistance to an array of harsh and changing exposures. Beyond the elements, due to the location of utilities, FRP composites
5. FRP PULTRUDED COMPONENTS: WHY 61
•
•
•
•
•
•
•
resist rotting, damage from termites, woodpeckers, and other vermin, making
it more durable and easier to maintain over time.
High Strength: FRP is stronger than many traditional materials used to
construct electrical and communication lines.
Lightweight: FRP poles are ideal for limited access sets requiring cranes and
hand or handsets.
Thermal Insulation: The thermal insulation characteristics of FRP is one of the
attributes that make FRP poles less susceptible to heat damage from chaparral
fires.
Electrical Insulation: As electrically non-conductive components, FRPs play
a crucially important role in regard to safety in the industrial applications
where grounding of currents is a safety concern. The high dielectric strength
of FRPs also improves worker safety while enhancing protections again
short-circuiting.
Resilience: FRP profiles are used in various utility infrastructure applications,
and when compared to those made from traditional materials, FRPs offer better
resiliency by ensuring that the utility supported by FRPs is up and running
with shorter downtimes after any interruption due to weather or unexpected
events. Event FRPs can also be formulated for fire resistance.
Design Flexibility: FRPs come in numerous shapes, sizes, and colors, allowing
projects to be tailored to unique specifications.
Speed of construction: FRP components in the utility sector allow for easier
transportation, handling, and fast installation, saving time.
5.7 FRP vs. TRADITIONAL MATERIALS
Traditional construction materials such as concrete, steel, aluminum, timber/
wood, have lost relevance giving way to durable, efficient, and highly engineered
FRP composite materials across many markets and industries, with the exception
of the construction industry. As with all the other FRP composites produced by
various available techniques, FRP pultruded components have proved their ability
to satisfy the cost, mechanical, physical, and environmentally resistant requirements while outperforming traditional materials. Moreover, the expanding interest
toward FRP composites materials in the built infrastructure is leading to the emergence and development of large, medium, and even small production lines on the
market.
This section provides a comparison between FRP pultruded component and
other traditional materials by normalizing the parameters used in the comparison.
5.7.1 Cost
The cost of FRP pultruded materials compared to traditional materials can vary
depending on several factors, including the specific application, size, and shape of
the component, required performance characteristics, and regional market conditions. An example of an indicative cost comparison between FRP and steel is
discussed later in this section.
It’s important to note that typically FRP pultruded components may have higher
upfront costs compared to traditional materials, nevertheless it is important to
account for the key attributes of FRPs offering long-term benefits such as durability, corrosion resistance, reduced maintenance, and improved lifecycle performance. Evaluating the overall cost-effectiveness of FRP versus traditional materials should consider not only the initial investment but also the long-term benefits
and savings associated with the specific application and project requirements, i.e.,
the cradle to grave approach, versus cradle to gate approach. For example, a cost
comparison between bridges made of FRP and bridges constructed by conventional methods is presented from cradle to grave is summarized in (Mottram and
Henderson 2018) [13]. Similarly, there have been other studies showing that when
considering the cradle to grave approach, the overall cost of ownership of a structure made from FRP pultruded components is significantly less than when using
traditional materials like steel [14], [15].
62
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
An indicative cost comparison of a 15m long and 2m wide pedestrian bridge
built of FRP and steel is summarized in Table 1. A lifespan of 120 years is considered. The total cost is divided into 4 groups: (i) acquisition cost, (ii) operation cost,
(iii) disposal cost, and (iv) salvage. The acquisition cost was higher for the FRP
bridge than for the steel version: the FRP material cost was about 40% higher than
steel but was slightly compensated with the lower transportation and installation
cost of FRP due to how lightweight it is when compared to steel. Also, due to the
lack of education and advanced resources to design FRP structures, the design and
certification process was cheaper for steel than FRP.
The main cost difference lies within the operation of the bridge. Because of the
non-corrosive nature and extended durability of FRP compared to steel, the maintenance cost during the service life of the bridge was considerably reduced: fewer
and less expensive inspections and repairs are expected when using FRP instead of
steel. This led to an overall reduction to the operational cost of about 60%, which
is a significant difference considering that the overall operational cost was around
5 to 6 times higher than the total acquisition cost. Finally, no big cost differences
were seen in the disposal or salvage cost.
Adding all the costs, it was concluded that in this particular project of a 15m long
and 2m wide pedestrian bridge, the total cost over a lifespan of 120 years was 45%
lower if FRP were used when compared to traditional steel, even though the initial
cost of acquisition was 40% higher for FRP than steel.
5.7.2 Weight
The weight (or density) of FRP pultruded sections is about one-quarter that of
steel, as seen on the first bar of the chart in Figure 58. This is especially beneficial for the transportation and installation of the pultruded sections. It also makes
the structure lighter once installed, which is key for projects, such as restoration
projects where not much load can be added to the existing substructure. Compared
to other lighter metallic materials like aluminum, FRP pultruded sections are also
lighter, with about a 25% lower density.
Table 1 - Cost comparison between bridges made of FRP and steel [13]
FRP footbridge
(£, K)
FRP footbridge
($, K)
Steel bridge
(£, K)
Steel bridge
($, K)
Design and certification
12
13
9
10
Indicative costs assuming 15 m footbridge 2 m wide (120 years design life)
A
B
Acquisition
Operation cost
C
Disposal
D
Salvage
Produce fee
100
108
70
76
Transportation
3
3
5
5
Install/commission
3
3
6
6
Inspection (GI and PI)
108
117
180
194
Inspection (SI)
24
26
80
86
Coating
30
32
240
259
Joints
20
22
20
22
Surfacing
25
27
25
27
Major maintenance
-
-
20
22
Traffic management
54
58
86
93
Project management
20
22
30
32
Decommissioning
25
27
25
27
Disposal
10
11
5
5
Material recycling
-
-
-5
-5
Total cost ownership
434
469
796
860
5. FRP PULTRUDED COMPONENTS: WHY 63
5.7.3 Tensile Strength
A comparison of the tensile strength of different materials is shown on the left
graph in Figure 59. It can be inferred that the tensile strength of unidirectional
pultruded elements is about 3 to 4 times higher than that of mild steel. On the right
graph in Figure 59, the specific tensile strength is presented based on the density:
since the density of FRP, as seen in the section before, is one-fourth of that of mild
steel and the tensile strength is about four times higher, the specific tensile strength
per density of FRP is around 16 times higher compared to mild steel.
5.7.4 Modulus of Elasticity
The modulus of elasticity of
pultruded unidirectional FRP is about
one-fourth that of mild steel, as seen
in Figure 60. This means that FRP
profiles have a lower rigidity and
experience higher deflections than a
steel profile with the same moment of
inertia. Thus, when designing structures made of pultruded FRP elements,
the serviceability limit state (deflection, etc.) tends to govern the design
rather than the ultimate limit state
(strength, etc.) since FRP has higher
tensile strength but lower modulus of
elasticity than steel.
Figure 58 – Density of various materials [16]–[22]
Figure 59 – Tensile strength (left) and specific tensile strength (right) of various materials [16]–[22]
Figure 60 – Modulus of elasticity (left) and specific modulus of elasticity (right) of various materials [16]–[22]
64
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
The right graph in Figure 60 shows the specific modulus considering the density
of the materials. Being the weight of FRP one-quarter of that of steel, the modulus
gets compensated to a point where the modulus per weight of the FRP is about the
same to the one of steel.
5.7.5 Shear Modulus
Pultruded FRP materials are anisotropic materials (have different properties in
different directions), while mild steel is isotropic (same properties in all directions). Since all the fibers (components with the FRP that provide strength and
stiffness) are longitudinally aligned, mechanical properties like strength and stiffness are significantly higher in the longitudinal direction than on the transverse
plane. The shear modulus measures the elastic shear stiffness of a material and
is defined as the ratio of shear stress to the shear strain. As seen in Figure 61, the
shear modulus of FRP materials is about 20 times lower than that of steel. Therefore, when designing structures with FRP, the shear adequacy and the connection
capacity of the section needs to be checked in detail.
5.7.6 Thermal Properties
Thermal properties of materials are key for certain applications. The left graph in
Figure 62 shows the transverse thermal expansion coefficient of various materials.
The thermal expansion coefficients of FRP are different in the axial and transverse
directions (because FRPs are anisotropic) and depend mainly on the fibers (axial)
and the resin (transverse). The longitudinal expansion is smaller than the transverse expansion because the thermal expansion of the fibers is less than that of the
matrix material [23]. In fact, the thermal expansion coefficients in the axial direction of most of the FRPs is negative [24]. The thermal expansion coefficient on the
transverse direction of unidirectional
pultruded FRP materials (shown in the
graph), however, is mainly governed
by the resin and is higher than steel.
The right graph in Figure 62,
however, shows the thermal conductivity of different materials. As
discussed throughout the report, FRP
material is thermally (almost) nonconductive, while mild steel, being a
metal, has a high thermal conductivity.
Therefore, FRPs are frequently used in
applications where heat transfer is an
issue, such as insulated panels, balconies, etc. to avoid thermal bridges.
Figure 61 – Shear modulus of various materials [16]–[22]
Figure 62 – Thermal expansion (left)) and thermal conductivity (right) of various materials [16]–[22]
6. FRP TESTING STANDARDS 65
6. FRP TESTING STANDARDS
Standard organizations around the world develop and publish different standard
test methods relevant to the use of FRP pultruded composite materials; two of the
most prominent international organizations are the ASTM International (ASTM)
and the International Organization for Standardization (ISO). Thousands of standardized test methods are available for testing the different constituent materials
used in FRP pultruded composites (fiber, resin, and additives), as well as FRP
pultruded elements at the lamina and laminate level. However, few standards are
available for testing FRP pultruded manufactured components at the full-section
level. Some of the organizations that have recently developed test standards
methods based on the FRP pultruded component application include the American
Concrete Institute (ACI), the European Committee for Standardization (CEN), the
Japan Society for Civil Engineers (JSCE), and the Canadian Standards Association
(CSA) [7].
To date, suppliers, manufacturers, structural engineers, owners, and other stakeholders involved in the use of FRP pultruded components do not have a universal
agreement regarding test methods applied to FRP pultruded components. The
focus tends to be segmented based on the application and market sector where the
FRP pultruded component is used. Nevertheless, some tests are available for the
materials constituents or selected FRP pultruded components because of the importance of physical and mechanical properties in design. The choice of the specific
test method is often left to the constituent material supplier, the FRP composite
material producer, or the FRP manufacturer. Test results are reported according to
the requirements of the standard test method chosen and can therefore be subject
to interpretation as to their relevance for the final structural engineering design.
As part of any construction project, a structural engineer will typically reference
material specifications for the FRP pultruded composites used in the project, for
inclusion in contract documents. The specification specifies the test methods to be
used and the FRP pultruded material properties that need to be reported. In addition, specific minimum or limiting values of certain properties are specified for the
FRP pultruded material, as these are typically dependent of the design assumptions. To this end, limits for FRP materials can be found in model specifications,
such as specifications for pultruded profiles published by the European Committee
on Standardization (CEN), and in the specifications for reinforced plastic ladders
published by the American National Standards Institute (ANSI). Chapter 7 of this
document will further discuss specification documents used in FRP pultruded
components and Chapter 8 relevant design documents.
Full-section test methods are useful for characterizing FRP pultruded manufactured components for structural engineering when coupon-type tests are not
feasible or limited based on the data derived, or due to the specimen’s size or
methods used. While full-section test methods have been developed to test FRP
pultruded composite products on a full scale for use in structural engineering, it is
important to note that testing at the fiber, lamina, and laminate levels is still necessary and required.
This chapter reviews the tests applicable to FRP pultruded composites for the
fiber, lamina, laminate, and full-section levels. Annex D provides a detailed list of
relevant test methods that are used in FRP pultruded composites, as discussed in
this chapter.
6.1 CONSTITUENT MATERIAL TESTS
6.1.1 Fiber
Fiber based tests are typically necessary for the FRP pultruder, and provided by
the fiber supplier, forming part of the material certification documents between
the fiber supplier and pultruder as client. Testing can be conducted on single fibers
taken from roving or tows using a single-fiber test method, such as ASTM C1557
or ASTM D3379, to obtain the basic properties of reinforcing fibers used in FRP
66
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
composites. However, single fiber testing may be difficult, and the data obtained
from tests on single fibers do not necessarily represent the properties as a bundle or
when used in FRP composite components. Consequently, fiber manufacturers may
also report the mechanical properties of fibers when impregnated with a commonly
used resin and tested as an FRP composite. As an example, the impregnated fiber
test used by glass and basalt fiber manufacturers is ASTM D2343, and the test
used by carbon fiber manufacturers is ASTM D4018. Fiber properties are then
calculated from the FRP composite test data using the rule-of-mixtures approximations. Some ASTM test methods referenced by fiber-based specifications include:
ASTM D1907, “Test Method for Linear Density of Yarn (Yarn Number) by the
Skein Method,” ASTM D2256, “Test Method for Tensile Properties of Yarns by
the Single-Strand Method,” and ASTM D4963, “Test Method for Ignition Loss of
Glass Fiber Strands and Fabrics.”
The characterization of the fibers is critical to determine the physio-mechanical properties of final composite components, while ensuring quality control and
quality assurance of manufactured FRP pultruded components, as the strength
of the fibers is the primary function of the overall strength of the FRP pultruded
composite material [7].
6.1.2 Resin
Many standard test methods for obtaining mechanical, physical, and chemical
properties of polymer-based resins (also known as plastics for this purpose) in their
liquid and hardened (cured) states are available from ASTM and other standard
organizations. These have been developed primarily by the plastics industry over
the past 50 years. It should be noted that the properties of the polymer are typically
obtained from tests on resin samples that have undergone a specific post-cured
protocol at elevated temperatures. This cure protocol may differ from the curing
protocol applied to a FRP pultruded components during manifesting. Tests for the
secondary constituents of the polymer matrix are reported similarly according to
ASTM or other industry-specific test methods [25].
These test methods are designed to provide accurate and repeatable measurements of various properties such as density, viscosity, gel time, tensile strength,
deflection temperature, flexural properties, impact resistance, adhesion, and abrasion resistance. The selection of a particular test method depends on the polymer
resin’s specific properties and the intended application. These test methods are
critical in ensuring the quality and performance of plastic products and are used in
various industries, including automotive, construction, aerospace, and electronics.
There are numerous organizations such as ASTM or ISO (International Organization for Standardization) and DIN (Deutsches Institut für Normung) who develop
test methods available for obtaining mechanical, physical, and chemical properties
of polymer resins in their liquid and hardened states. It is important to select the
appropriate test method based on the specific properties of the polymer resin being
tested and the intended application. Some commonly used ASTM test methods for
plastics include:
• ASTM D792 – Standard Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement;
• ASTM D638 – Standard Test Method for Tensile Properties of Plastics;
• ASTM D648 – Standard Test Method for Deflection Temperature of Plastics
Under Flexural Load in the Edgewise Position;
• ASTM D790 – Standard Test Methods for Flexural Properties of Unreinforced
and Reinforced Plastics and Electrical Insulating Materials;
• ASTM D256 – Standard Test Methods for Determining the Izod Pendulum
Impact Resistance of Plastics;
• ASTM D3359 – Standard Test Methods for Measuring Adhesion by Tape Test;
and
• ASTM D4060 – Standard Test Method for Abrasion Resistance of Organic
Coatings by the Taber Abraser.
6. FRP TESTING STANDARDS 67
6.2 FRP MATERIAL TESTS
Many tests conducted on FRP pultruded composites for structural engineering
applications are conducted on coupons extracted from the as fabricated FRP
pultruded composite component. When these tests are conducted on coupons cut
from an FRP pultruded composites containing only unidirectional fibers the testing
conducted is of a unidirectional ply (i.e., on the lamina level). When the coupon
is cut from an FRP composite that contains multidirectional plies or mats (such as
FRP profiles), testing is on a multidirectional plate (i.e., on the laminate level.) Test
coupons from the as manufactured component should contain the full thickness of
the FRP component to obtain the necessary design dependent properties.
When determining properties of FRP pultruded composites on either the lamina
or laminate level, typically the same test standard methods are used since the test
is conducted on the macroscopic level and assumes, for the purposes of conducting
the test, that the coupon is made of a homogenous material. Standard tests methods
for strength, stiffness, and physical dependent properties commonly used for
FRP lamina or laminate are given in Table 2. The physical tests noted should be
conducted on samples taken from the as fabricated FRP composite, and not on
Table 2. Standard Test Methods for FRP Composites at the Lamina and Laminate Level
Ply or Laminate Property ASTM Test Method(s) Test Required
ASTM Test Method(s)
Test Required
Strength Dependent Properties
Longitudinal tensile strength
D 3410, D 695
Longitudinal compressive strength
D 953, D 5961
Longitudinal bearing strength
D 2344, D 4475
Longitudinal short beam shear strength
D 5379, D 3846
In-plane shear strength
D 256
Unidirectional ply and multidirectional laminate
Impact resistance
Transverse tensile strength
D 3039, D 5083, D 638
Transverse compressive strength
D 3410, D 695
Transverse short beam shear strength
D 2344
Transverse bearing strength
D 953, D 5961
Multidirectional laminate only
Stiffness Dependent Properties
Longitudinal tensile modulus
D 3039, D 5083, D 638, D 3916
Longitudinal compressive modulus
D 3410, D 695
Major (longitudinal) Poisson ratio
D 3039, D 5083, D 638
In-plane shear modulus
D 5379
Transverse tensile modulus
D 3039, D 5083, D 638
Transverse compressive modulus
D 3410, D 695
Unidirectional ply and multidirectional laminate
Multidirectional laminate only
Physical Dependent Properties
Fiber volume fraction
D3171, D2584
Density
D792
Barcol hardness
D2583
Glass transition temperature
E1356, E1640, D648,
E2092
Water absorbed when substantially saturated
D570
Longitudinal coefficient of thermal expansion
E831, D696
Transverse coefficient of thermal expansion
E831, D696
Dielectric strength
D149
Flash ignition temperature
D1929
Flammability and smoke generation
E84, D635, E662
Unidirectional ply and
multidirectional laminate
68
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
samples taken from the polymer matrix alone – which is sometimes the case. This is
because the fiber can have an influence on many of the physical properties that are
often assumed to be a function of the resin alone, such as the hardness, glass transition temperature, and flash ignition temperature. Table 2 contains the reference
of a standard guide to testing of FRP composite materials that can be consulted,
ASTM D4762. This guide also provides test methods for additional properties of
interest to structural engineers, such as creep, fatigue, and fracture properties of
FRP composites. Additional guidance on conducting tests on composite material
unidirectional and multidirectional laminates may be found in the publication by
Carlsson and Adams [25]. It should be noted that many of these tests are also used
to evaluate durability properties of FRP pultruded composites after exposure to
applicable environment or accelerated conditioning protocols (based on the FRP
application).
6.2.1 Lamina Level
The distinction between testing the unimpregnated dry fiber level and the
impregnated roving on the lamina level is of particular importance for the structural engineer in the design of FRP strengthening systems. Guides typically allow
for two different methods for designing FRP strengthening systems.
One method uses the properties of the FRP composite, which are calculated
using the measured gross area of the FRP composite; the other method uses the
properties of the fibers, which are calculated using the manufacturer-supplied area
of the fibers in a dry sheet or fabric. However, according to other design based
documents (for example ACI 440.3R-04, Test Method L.2), when the area of the
fiber method is used, the fiber properties are not obtained from single-fiber tests.
For either design method both the longitudinal strength and stiffness of either the
FRP composite or the fibers are obtained from a test on the FRP composite at the
ply level. Consequently, the methods lead to identical designs.
6.2.2 Laminate Level
As noted above, the test methods used for a multidirectional laminate are technically the same as those used for a unidirectional FRP, as shown in Table 2. However,
two key differences should be noted when used for multidirectional composites.
First, only longitudinal mechanical tests are conducted on the unidirectional ply,
while multidirectional laminates require both longitudinal and transverse tests. In
some cases, other test directions are also evaluated based on application. Second,
the exact requirements of the ASTM standard test methods cannot always be satisfied, due to the thickness and construction of the FRP component (e.g.using fabric
and mat layers). ASTM D6856 provides recommendations on the modifications
that need to be made to the standard test methods when fabric-type composites are
used, where this type of FRP composites tend to be thicker than traditional unidirectional composites.
6.2.3 FRP Pultruded Components
Often, lamina/laminate level testing is combined with testing on a segment of the
FRP pultruded component, to determine several physio-mechanical and durabilitybased properties such as tensile, compressive, flexural, toughness, and shear properties. Below the most tested physio-mechanical properties are listed, and Table 3
summarizes the main test methods.
Tensile Tests: These tests are used to determine the tensile modulus, Poisson’s
ratio, tensile strength, and ultimate tensile strains. Specific details of the tensile
test can be found in ASTM D3039, ASTM D638, and ISO 3268 standard tensile
testing protocols. The mode of failure will usually be in fiber fracture or fiber
pullout when the sample is tested with fibers in the longitudinal direction, while
matrix or fiber–matrix interface failure will usually govern with fibers tested in the
transverse direction [23].
Compressive Tests: Used to determine the compressive modulus, Poisson’s ratio,
compressive strength, and ultimate compressive strains. The compressive tests can
6. FRP TESTING STANDARDS 69
Table 3 – Tests to determine physio-mechanical properties of FRP components
Mechanical properties
Method
Fire
Bearing Load
ASTM D1602
Compressive Strength
and Modulus
ASTM D695
Surface Burning
Characteristics
Tensile Strength
Method
ASTM E84
ASTM D162
ASTM D6641
Oxygen Index
ASTM D2863
ASTM D3410
NBS Smoke Test
ASTM E662
ASTM C365
Multi-Story Building Test
NFPA 285
ISO 844
Room Corner Test
NFPA 286
ASTM D638
Ignitability by Radiant
Panel
NFPA 268
ASTM D3039
Potential Heat of Building
Materials
NFPA 259
ASTM D5083
Cone Calorimeter
ASTM E1354
ASTM C297
Tensile Modulus
Elongation
DIN 53455
Surface Testing
Method
ASTM D638
Gravelometer
SAE J-400
ASTM D3039
Gardener Gloss Meter
GARDNER
ASTM C297
Stain Resistance
ANSI Z124
DIN 53457
Bracol Hardness
ASTM D2583
Physical Properties
Method
ASTM D638
ASTM D3039
Flexural Strength and
Modulus
Flexural Strength and
Stiffness
ISO 1922
Specific Gravity
ASTM D792
ASTM D790
Water Absorption
ASTM D570
ASTM D6272
Glass Transition
ASTM D7028
ASTM C393
Coef. Thermal Expansion
ASTM E289
ASTM D7249
Heat Distortion
ASTM D648
ASTM D7250
Punch Shear Test
ASTM D732
In-Plane Shear Strength
and Modulus
ASTM D3518
Brookfield Viscosity
ASTM D2196
ASTM D3846
Ignition Loss of Cured
Reinforced Resins
ASTM D2584
ASTM D5379
Gel Time
ASTM D2471
ASTM D4255
Glass Fiber Strands
ASTM D578
ASTM D3914
ASTM D7078
ASTM C273
ASTM C393
ISO 1922
Lap Shear Strength
ASTM D3164
Short Beam Strength
ASTM D2344
Izod Impact
ASTM D256
Charpy Impact
ASTM D256
Bearing Strength
ASTM D953
be carried out per ASTM D3410, ASTM D695, and ISO 8515 testing standards,
among others. Depending on the type and modulus of the matrix system used, the
mode of failure can be (1) micro buckling of fibers, (2) transverse tension failure or
fiber splitting, and (3) compression failure of the reinforcement. The compressive
properties are obtained using compressive load–displacement test data. Compres-
70
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
sive tests may also be carried out on test specimens that have been subjected to
prior impact load to determine the effect of delamination caused by such loads.
Shear Tests: Used to determine the shear modulus, shear strength, and ultimate
shear strains. The most used shear test is the short-beam shear test per ASTM
D2344 and ISO 4585. The desired failure mode for this test is due to interlaminar
shear failure between the plies. This typically occurs when the specimen has a
support span/thickness ratio of around 4 to 5 and is loaded in three-point bending.
However, since the specimen is not loaded in uniform shear, it is difficult to reliably determine the shear properties. Thus, this is used more as a quality control
test to determine interlaminar shear strengths between specimens. Other shear tests
used to determine the shear properties of composites include the double-notched
shear test (ASTM D5379), double-cantilever beam test, and rail shear test (ASTM
D4255).
Flexure Tests: Used to determine the flexural strength and modulus of the
composite. The test is similar to the interlaminar shear test, carried out using a
three- or four-point fixture (ASTM D790). The support span/thickness ratio in
these tests is usually much larger to reduce the interlaminar shear deformation and
to ensure failure is in flexure. Since a flexural failure is due to a combination of
tensile and compressive forces, it is difficult to extract any inherent properties from
the flexure tests and they are used more as a quality control tool.
Toughness Tests: May be carried out for quality control and to estimate the crack
propagation and delamination characteristics of a composite sample under impact
loads. The Izod and Charpy pendulum impact tests and the falling dart impact test
are most used.
Fire Performance: ASTM E84 is the standard test method for assessing the
surface burning characteristics of building products to observe the flame spread
and developed smoke density. And another test UL 94, the Standard for Safety
of Flammability of Plastic Materials for Parts in Devices and Appliances testing,
is a plastics flammability standard released by Underwriters Laboratories of the
United States. The standard determines the material’s tendency to extinguish or
spread the flame once the specimen is ignited. An increased viscoelastic response
is observed for composite materials exposed to elevated temperatures where resins
or adhesives are softened. In addition, the softening of the polymer is associated
with a reduction in mechanical properties and increased rates of moisture diffusion, which can accelerate damage mechanisms of the polymer. Some elevated
temperature effects can be beneficial, such as post-cure of resins; however, with
the combination of high temperatures and moisture immersion, the residual effects
of post-cure can be negated by rapid deterioration. Furthermore, when composite
materials are exposed to high temperatures (>100°C), the matrix softens leading to
distortion, buckling, and potentially failure of load-bearing elements. At temperatures in the range of 250°C–400°C, near the pyrolysis temperature of the matrix,
ignition of the composite can occur [23].
Moisture Properties: Moisture can cause reversible and irreversible changes in
composites through mechanisms such as hydrolysis, plasticization, saponification,
and others. In particular, moisture absorption causes plasticization, characterized
by a decrease in the glass transition temperature (Tg), and mechanical properties
of the polymer matrix. This is primarily caused by the interruption of Van der
Waals bonds between polymer chains and contributes to the decrease in the matrixdominated properties of a composite. This behavior has been observed in epoxy,
polyester, and vinyl ester resins, which are the most often used in composite materials for construction [26]. Other influences of moisture include the swelling of
the matrix region, which can induce stresses like thermal responses and result in
microcracking in the matrix, again leading to a decrease in matrix-dominated properties. In some instances, the moisture can wick along the fiber matrix interface
and induce interphase cracking, resulting in debonding between fiber and matrix.
Debonding between fiber and matrix can lead to premature failure of the composite
in the fiber direction and loss of load transfer across fibers. Furthermore, glass fibers
are known to degrade when exposed to moisture. This degradation is initiated by
6. FRP TESTING STANDARDS 71
moisture-extracting ions resulting in a potential loss of thermo-mechanical properties of the fibers. Also, since aramid fibers are polymers, they can absorb moisture,
eventually resulting in the fibrillation of the fibers. Carbon fibers, however, do
not absorb moisture and are resistant to chemical attack making them particularly
robust in changing environmental conditions characteristic of civil infrastructure
[27].
Acid/Alkaline Exposure: With the high usage of FRP composites in applications
across the full range in the pH scale from acidity to alkalinity, tests of composites exposed to solutions with varying levels in pH as high as 13.5 [26] are also
performed. The influence of the acidity/alkaline environment depends on the matrix
and fibers used in the composites. Dry glass fibers are particularly susceptible to
alkaline attack, inducing greater levels of irreversible damage, which are characterized by high levels of fiber surface degradation and pitting. When exposed to
alkaline environments, glass fibers can also undergo leaching, where alkali ions
diffuse out of the glass structure essentially dissolving the fiber. Acid or alkaline
solutions are known to cause degradation of the resin and interphase thus the need
to validate that the formulation used in the FRP composites meets the durability
application needs [23], [28].
UV Radiation Exposure: Polymers used in outdoor applications are susceptible
to photo-initiated oxidation leading to surface degradation. While this degradation
is usually confined to the top few micrometers of the FRP composite surface, flaws
from the surface can cause stress concentrations and result in premature fracture.
UV radiation is a component of the natural weathering process and is often accompanied by changes in temperature, moisture, chemical agents, and microorganisms. To protect against UV radiation, FRP composites will typically have a resin
formulated to be UV resistant or protected by a coating or gel coat. These serve
as a sacrificial layer to prevent the FRP composite from being directly exposed to
UV. The protective coating requires routine maintenance because it is not resistant
to UV radiation degradation [23], [26].
Fatigue: A mechanical-durability property that also needs to be evaluated for
FRP composites based on its application includes fatigue, where period cycles
of loading and unloading is applied, and/or coupled with environmental fatigue,
which involves temperature cycles (i.e., hot–cold, freeze–thaw), and/or chemical
cycles (i.e., moisture, seasonal road treatments, oxidation, NOx effects) [26],
[27]. Fatigue in composites is progressive and accumulative in nature, as opposed
to crack growth behavior observed in metals. Under fatigue loads, composites
can experience microcracking, delamination, fiber fracture, and fiber/matrix
debonding. In general, it has been observed that composites with higher modulus
fibers display greater fatigue resistance; hence, carbon fibers exhibit slower stiffness and strength degradation under fatigue.
Creep and Relaxation: This type of effect is mostly a fiber-dependent property.
The occurrence of creep in polymeric composites can be attributed to a combination
of bulk material strain and microflow initiation (such as fiber–matrix debonding
and cracking); both mechanisms are time-dependent due to the viscoelastic nature
of the polymer. Aramid and glass fibers are known to have higher susceptibility to
creep rupture at lower stress levels than carbon fibers. Basalt fibers have significantly better creep behavior than glass or aramid but slightly lower than carbon.
Under-cured composites have a higher susceptibility to creep and microcrack initiation at the early stages of service [23].
6.3 FULL-SECTION TESTS FOR FRP PROFILES
Generally, FRP pultruded profiles are designed using the properties obtained
from the coupon tests and use of appropriate theoretical coefficients. Nevertheless,
the use of full-section tests on individual profiles or on subassemblies of profiles to
develop full-section properties is also done. This is because there are situations in
which a full-section property is easier to use in a design or when coupon property
data cannot be used confidently to predict the performance of complicated details,
or when complex fiber architecture or composite construction is used.
72
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Since designs of pultruded profiles are often controlled by serviceability and
buckling criteria, the full section’s bending, transverse shear, and torsional rigidities (EI, GAs, and GJ) are needed in the design. Although theoretical methods are
available to predict these properties from coupon data, the designer must make
several simplifying assumptions related to the profile’s geometry, homogeneity,
and anisotropy. Full-section testing is a way of obtaining an effective and reliable
property for a profile that can be used in a stress-resultant theory.
The most widely used full-section test is the test for the full-section modulus, or
E-modulus as most manufacturers refer to it. The FRP pultruded profile is tested in
three- or four-point bending and an effective longitudinal modulus is determined
from load and midspan deflection data (CEN Part 2 Annex D) [29]; however,
due to the presence of shear deformation effects in pultruded profiles because of
moderately high longitudinal-to-shear modulus ratios (4 to 6 for glass-reinforced
profiles) and because pultruded profiles are generally used on shorter spans than
steel beams, the results of the full section bending test need to be interpreted
with caution. As noted in the CEN test method, the effective flexural modulus is
a span-dependent property, due to the effect of shear deformations. To minimize
the effects of the shear deformation, the CEN test method requires the profile to
be tested over a span-to-depth ratio of at least 20. In addition, the measured value
of the full-section modulus obtained from the test is multiplied by a factor of 1.05
to compensate approximately for the effects of shear deformation. This test does
not yield the full-section transverse shear rigidity (GAs) often needed in a design
where a shear deformation beam theory is used to predict deflections.
CEN Part 2 Annex G provides a method to measure a profile section’s bending
rigidity (EI) and shear rigidity (GAs) simultaneously by testing it on different span
lengths and performing a data analysis. This method has been used by several
researchers and manufacturers to obtain results that can be used in design and had
become a de facto standard prior to publication by CEN. CEN Part 2 Annex G also
provides a method to determine the full-section torsional stiffness of an FRP profile
using a fixture that applies a uniform torsional moment to the profile and measures
the rotation. It is important to note that the torsional stiffness thus obtained is the
unrestrained or non-warping restrained torsional stiffness (also known as the SaintVenant torsional stiffness). In most structural engineering applications, the ends of
the structural members are restrained against warping and the warping torsional
constant (ECw) is needed for design. This can be measured in an indirect method
using a nonuniform torsion test. It should also be noted that singly symmetric
open-cross-section FRP profiles have very low torsional rigidity and should not
be used when significant torsional moment carrying resistance is needed. FRP
pultruded profiles must be laterally braced when used as beams and columns to
prevent lateral or torsional instability under bending or axial loads.
Full-section tests to determine the strength and stiffness of connections in
pultruded structures are not standardized. Most manufacturers of pultruded profiles
provide load tables for simple framing connections. These tables are based on full
section testing of subassemblies of profiles conducted using undisclosed in-house
methods. Data is generally not provided on failure modes or deformations nor
correlated with coupon property data obtained from bearing tests. Neither is there
a standard procedure for full section testing of semirigid connections for pultruded
frame structures that are needed to obtain strength and moment–rotation characteristics for these connections to analyze frames with semi-rigid connections [7].
6.4 NON-DESTRUCTIVE TESTS
Non-destructive tests (NDT) are typically used to evaluate composites in-situ,
where conventional testing and inspection procedures are not sufficient to evaluate and quantify possible defects in the composite components. Therefore, nondestructive evaluation technologies, tests, and structural health monitoring play a
significant role in assisting infrastructure owners in assessing the condition of FRP
structures. This field is rapidly progressing as the use of FRP materials becomes
more widespread to address primarily in-service inspections.
6. FRP TESTING STANDARDS 73
NDT also has a role in the quality assurance of FRP applications. Several
approaches have been described in this chapter for evaluating debonding of an
FRP laminate to a concrete or steel structure. Determining the strength of that bond
in a nondestructive manner remains an elusive goal for both civil and aerospace
structures. Ultrasonic methods have explored the evaluation of material properties
of composite materials in a nondestructive manner, but fieldable technologies are
yet to emerge.
Overall, applying NDT to evaluate civil structures is a growing field in research
laboratories and practice. Table 4 summarizes available NDT as discussed in this
chapter and their primary application to detect various deterioration or damage in
FRP composites. As seen, no single NDT is suitable for all failure or deterioration
modes, and as is frequently the case, several NDT may be employed to achieve a
comprehensive condition assessment of a particular FRP structure. It should also
be noted that the table indicates the primary applications for the technologies;
some of the techniques could be used for other deterioration modes if properly
developed. All the NDE technologies within this section mostly characterize local
defects and do not indicate strength or durability. Load testing is predominantly
used for such applications. Future application of NDE technologies to composites used for civil infrastructure will improve the quality of construction, and as
the existing infrastructure ages, help support effective repair and renovation of
composite structures [23].
Delamination in
Subsurface Concrete
Bond Strength
Debonding Between
Composite Layers
Delamination of
Composite from Substrate
Loss of Mechanical
Properties
Fiber Breakage
Fibrillation Unraveling
and Broken Fibers
UV Damage
Moisture Absorption
6.4.1 Visual Inspection Testing
The most rudimentary method of inspecting FRP composites is by visual inspection. Visual observations of condition provide fundamental data on the performance and condition of the material, provided adequate procedures are developed
and validated as part of the inspection process. A significant advantage of visual
inspection testing is its low cost and simple application. Standardized training in
detecting and documenting the deterioration modes such as unraveling, debonding
at edges, UV damage, and absorption of moisture can enable an effective inspection
to be conducted. Unfortunately, this type of testing is unable to detect subsurface
deterioration. A visual inspection can be combined with sounding (as discussed
next) to improve the inspector’s
ability to assess the condition of the
Table 4 - Summary of NDT technologies and typical applications [23]
composite. An in-depth visual inspection for an FRP pultruded structure
requires that the structure is inspected
by a certified inspector. For bridges,
Technique
this commonly requires specialized
access equipment that can add significant cost to the inspection.
Microcracking in the outer resin
layers can be symptomatic of moisVisual inspection
X
X
X
ture absorption into the composite
resulting in the expansion of the
Sounding
X
X
X
resin and deterioration of the resin/
fiber bond. Under severe situations, a
Infrared Thermography
X
X
X
general, widespread expansion of the
matrix material or localized blistering
Microwaves
X
X
X
may be evident due to water absorption. The appearance of moistureUltrasonic pulse-echo
X
X
X
X
X
induced deterioration of GFRP mateAcousto-Ultrasonics
X
X
X
X
X
rials can be characterized by white
lines appearing on the surface due to
Guided waves
X
X
X
X
X
cracking between the glass fibers and
the matrix [30].
Acoustic Emission
X
For Aramid/Kevlar
materials,
discoloration of the materials may
74
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
indicate photooxidation, that is, UV damage. This condition may exist in the top
layers of material, but it is generally believed that the depth to which this damage
can be extended is limited by the relatively low energy of the photons causing
the damage. However, UV damage in the surface layers may allow for moisture
penetration into the composite materials, deteriorating the fiber-matrix bond and
reducing the strength of the composite materials.
6.4.2 Sounding Testing
It is a simple test method for searching for delamination and deboned areas by
mechanical sounding. This method consists of using a metal or plastic hammer
type object to strike the surface of the composite material while listening to the
tone of the impact. Delaminated areas can frequently be located from their distinctive hollow tone. Sounding has been implemented for aerospace structures utilizing
a quarter, and hence, is commonly referred to as a coin-tap test. The low mass of a
coin results in a high-pitched tone that can reveal delamination between composite
layers and possibly between the composite and the bonded substrate. For deeper
features, a larger mass should be used such that the depth of the material is excited
by the tapping. The use of hammers allows for the detection of features further
from the surface, but near-surface features such as delamination between layers of
FRP composite may be obscured [31].
Research has been conducted to evaluate the quantitative aspects of sounding
methods. Areas of FRP composite with embedded damage or debonding can be
expected to have a lower stiffness than intact areas, and this lower stiffness results
in the dull, low-frequency tone. This effect can be measured using an accelerometer mounted on the tapping device. The accelerometer measures the width and
amplitude of the impact pulse. The width of the pulse is sensitive to the stiffness
of the material being impacted, whereas the amplitude of the pulse is sensitive to
the velocity of the device during impact. Testing revealed that the pulse width was
relatively insensitive to the velocity at impact, except for very low velocities, and
this pulse width could be used to determine the structural stiffness of the material
as well as reveal the location of subsurface defects.
6.4.3 Ultrasonic Testing
This NDT technique is commonly used to inspect the internal structure of FRP
composite materials. This is based on a simple principle of wave physics (see
Figure 63). A high-frequency sound wave that has been generated by a small probe
called a transducer and coupled into a solid medium like fiberglass or composites
will travel in a straight line perpendicular to the surface until it encounters a material boundary such as a far wall, another material interface, or a lamination [32].
At that point, the sound wave will be reflected in a predictable way. Thickness
gages measure the round-trip transit time of the sound pulse and then use the
programmed speed of sound in the test material to calculate thickness. Ultrasonic
flaw detection analyzes echoes through a comparative process in which the echo
pattern generated by a good part is compared with the echo pattern from a test
piece.
Since sound waves will reflect from voids or cracks, changes in the echo pattern
indicate changes in the internal structure of a part. In testing fiberglass and composites, the instrument typically looks for the presence of echoes within a marked gate
or window that represents the interior of the test piece (see Figure 64). While the
inhomogeneous nature of composites can generate scatter noise reflections even
from solid material, cracks whose area approaches the diameter of the sound beam
typically return strong localized indications that will be recognized by a trained
operator [32].
6.4.4 Vibrational (modal) Testing
Vibrational testing is an inspection method that uses the natural frequency and
modal characteristics of the FRP composite to locate defects. The FRP composite
part is subjected to continuous or pulse excitation, through an automated shaker or
6. FRP TESTING STANDARDS 75
impact hammer, and accelerations are recorded, which can then be converted into
a natural frequency spectrum and mode shapes using vibrational analysis methodologies. These can then be compared to reference frequencies and mode shapes of
a defect-free sample to qualitatively determine the presence of defects. If the information is recorded over the entire surface of the part through well-placed accelerometers, the reference and actual vibrational characteristics can be processed by
automated NDT defect detection algorithms and numerical procedures to locate a
defect and quantify its damage severity [23].
6.4.5 Infrared Thermographic Testing
This testing inspection method relies on the thermal diffusion rate to locate a
defect within the FRP pultruded composite. In this inspection method, the FRP
composite part is first subjected to heat on the surface either through a high-intensity flash heat impulse (such as a xenon flashbulb) or through gradual heating using
a lightbulb or ambient heating (see Figure 65). The sample may also be heated
uniformly in an oven and the heat loss upon cooling may be monitored. Flash
impulse heating is usually preferred since the amount of heat input can be monitored and replicated between samples. It also uses a portable system that can be used
for periodic inspection during the manufacturing process. The rate of heat diffusion
is different through different materials and depends on the density of the material through which it passes. Thus, in the presence of a defect that has a different
density than that of the composite, there will either be a buildup of heat (hot spot)
in defects such as air voids or absorption of heat (cold spot) at locations
of defects such as uncured resin or
entrapped moisture. A thermographic
camera can record the thermal gradients over the surface of the composite.
Defects can be identified by peaks
or troughs in the thermal gradient.
Using image processing software
that captures the camera’s data over
time, it is possible to determine the
location and severity of the defect
quantitatively. The resolution of the
thermographic image is usually lower
than that of ultrasonic or radiographic
Figure 63 – Principle of ultrasonic testing a composite material in transmission
inspections, particularly for unidimode [33]
rectional fiber pultruded composites
in which the heat conductivity in the
fiber direction is much greater than
that in the thickness direction. The
portability of the system and the relative ease of using it in a factory setting
make it an attractive tool for quality
control of FRP composites [23].
6.4.6 Acoustic Emission Testing
This testing and inspection method
detects defects by “listening” to
how sounds are propagated by the
FRP composite when it is stressed
either through mechanical or thermal
loading. The sounds are emitted
due to micro-failures such as individual fiber fractures and progressive
matrix micro-cracking. The number
of acoustic ‘events’ over sustained
Figure 64 – Testing of fabricated carbon fiber composite for cracking and
laminar defects with an ultrasonic flaw detector (Source: Olympus)
76
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
loading will be much greater for an
FRP composite part with defects.
However, currently it is very difficult
to quantify the location and severity of
defects using this method particularly
in a factory setting [23].
6.4.7 Acoustic-Ultrasonic
Testing
This NDT method combines
acoustic and ultrasonic testing, and
is used to determine the severity of
internal imperfections and inhomogeneity in FRP composites. It allows noncritical flaws to be seen and assessed.
It also indicates accumulated damage
Figure 65 – The measuring head contains a highly sensitive infrared camera with
in a structure due to fatigue loading or
integrated control electronics and a heat source (halogen lamp) with integrated
impact damage. The disadvantage of
power electronics.(Source: Automation Technology)
this type of inspection is the mandatory setup and pre-calculations before
any testing. Another disadvantage is
that this type of testing is not useful for detecting large individual flaws such as
delamination or voids [34].
6.5 QUALITY CONTROL AND QUALITY ASSURANCE
The mechanical characteristics and surface appearance of composites are
contingent on the production process, equipment quality, and inspection methods
employed during manufacturing. Quality control and quality assurance (QC/QA)
testing thus forms an integral and significant part of the manufacturing process of
FRP pultruded composites to obtain consistent, high-quality components. Effective QC/QA for FRP composite components depends on careful and systematic
monitoring of the design process, the manufacturing tools and equipment, and the
finished quality of the manufactured composites.
The first step of QC/QA begins with validating the critical design, geometric,
material and manufacturing parameters assumed by the designer and comparing
those parameters with the manufacturing plant’s tooling, assembly, equipment, and
labor constraints. Weight, cost, and productivity concerns are considered to ensure
that an optimized design and manufacturing methodology has been chose. The
second QC/QA step involves verifying the tooling and mold dimensional tolerances, equipment and controller calibrations, assembly stability and fabrication/
handling processes. Component tests on the tooling assembly may include tests to
validate aerodynamics, vibroacoustic, mechanical, and thermal loading conditions
during manufacturing. Tests on subcomponent tool parts may include tensile and
compressive coupon tests and damage tolerance tests. The third step of QC/QA
includes quality control of the manufactured FRP composite component through
inspections and/or destructive/nondestructive testing over the entire manufacturing
process. The main components of this step include:
• Validation and characterization of the properties of the constituent materials
used to manufacture the FRP pultruded composite;
• Monitoring the curing and post-cure process of the FRP composite; and
• Validating the physical and mechanical properties of the finished composite.
Visual inspection testing is used to detect any visible surface discontinuities
and/or delamination. Mechanical inspection and testing are used to verify design
dimensions and mechanical properties of the individual constituents as well as the
manufactured composite part in its entirety. Numerical simulation and study of
cure kinematics may be performed to monitor the curing process. NDT evaluation
is used for determining defects and anomalies in the composite part and can be
used as the final quality control tool before the part is shipped out. The aforemen-
6. FRP TESTING STANDARDS 77
tioned quality control is deemed necessary to ensure that the manufactured part
consistently meets the design specifications and is necessary to obtain ISO 9000
certification for the product [23].
Below is a simplified QC/QA procedure for manufacturing FRP pultruded
composites. During the manufacturing process, quality controls may include
the visual checking of the components of the pultrusion line (creels, forming or
performing guides, resin bath), and the monitoring of several process parameters,
as follows [35]:
• Ambient temperature and humidity;
• Temperature of the resin wet bath;
• Temperature control at different points inside the die, together with the evolution of material temperature along the die (with thermocouples);
• Pultrusion speed;
• Clamping and pulling forces (with load cells);
• Resin injection pressure and flow (when resin injection systems are used); and
• Product length.
QC/QA of FRP pultruded components can be implemented according to a recognized quality control scheme and may be documented in the form of a certificate
of conformity. This can include both the general obligatory properties according
to a specific standard (e.g., EN 13706–2,3 [36]) and extra properties agreed upon
with the customer. At this stage, QC/QA should address at minimum the following
aspects: visual defects, dimensional tolerances, and mechanical properties (based
on application).
Several defects of pultruded parts can be inspected visually as previously
discussed. Annex A of the EN 13706–2 standard specifies the definition and the
acceptance levels of the following defects, which can be assessed by the unaided
eye at a distance of about 20 in. (0.5 m) [36]: blister, crack, crater, delamination,
die parting line, dullness, exposed underlayer, fiber prominence, folded reinforcement, fracture, grooving, inclusion, internal dry fiber, internal shrinkage cracks,
internal porosity (voids), surface porosity (voids), resin-rich area, saw burn, scale,
stop mark, under cure, and wrinkle depression. The same is recommended in
ASTM D4385 standard for thermosetting reinforced plastic pultruded rods, bars,
shapes, and sheets, in which different inspection requirements are specified for
three product quality grades.
In terms of cross-section geometry, Annex A of EN 13706–2 [36] specifies
dimensional tolerances for the following geometrical parameters: wall thickness
of open and closed profiles, flatness in the transverse direction, profile height and
width of flange, size of angle, straightness, and twist. Similar specifications are set
out in ASTM D3917 standard for rods, bars, and FRP pultruded shapes made of
thermosetting glass-reinforced plastics.
Several pultrusion companies use Barcol hardness testers to assess the degree of
cure of the produced parts. This enables the tracing of products with an insufficient
degree of cure of the resin matrix, which leads to lower mechanical performance.
The quality control of pultruded-produced parts can also include other mechanical
characterization tests, which can sometimes be carried out within the laboratory
facilities of pultrusion companies. EN 13706–3 [36] defines two grades of FRP
pultruded profiles, specifying minimum values for material properties and the
relevant test methods. The requirements for certain applications (e.g., petroleum
and natural gas industries) can be stricter and often include aspects related to fire
performance (e.g., NBR 15708–1 [37]).
In addition, the American Composites Manufacturers Association (ACMA) has
also published the Code of Standard Practice for Fabrication and Installation of
Pultruded FRP Structures [38]. This code includes a comprehensive section on
quality control (QC) and quality assurance (QA), encompassing various critical
aspects. It covers conformance to design and specifications, material inspection, fabrication inspection, internal auditing, and applicable testing procedures
for support of structural design. These guidelines ensure that the FRP pultruded
78
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
sections meet the required standards and specifications, thereby enhancing the reliability and integrity of the structures they are used in.
7. FRP PULTRUDED SPECIFICATIONS 79
7. FRP PULTRUDED SPECIFICATIONS
7.1 PURPOSE OF SPECIFICATIONS
A specification is a document that typically defines an explicit set of requirements to be satisfied by a material, product, system, or service. In this chapter of the
document, several different types of FRP specifications will be reviewed, including
references to specific published specifications, to assist stakeholders in implementing the use of FRP pultruded composite solutions in the built infrastructure.
These specifications play a critical role in the implementation of FRP composites
for various reasons in different industries and applications. The primary purposes
for the need of specifications for FRP pultruded components are highlighted below:
7.1.1 Performance and Quality
Specifications outline the specific properties and characteristics of a material
required for a particular application. This may vary from geometrical, physical, to
mechanical and durability-based properties, as well as other application specific
characteristics to ensure safe and reliable operation. Specifications ensure that the
both the constituent materials forming part of the FRP pultruded component, as
well as the final component will perform to the required standards. It is important to note that performance-based specification will typically state the minimum
requirements, but in many cases manufacturers will provide FRP composites that
exceed the minimum specification requirements.
7.1.2 Safety and Reliability
Material specifications play a crucial role in ensuring the safety and reliability
of the FRP pultruded composite. By specifying certain properties, materials and
performance requirements, the final manufactured components can be selected
and tested to meet safety regulations and minimize the risks of failure for a given
application. To this end, specifications will include sampling requirements, which
specify the number of test repetitions and the testing required between production
lots or other variables. These requirements are used to derive property values from
the test results, which are then employed for design purposes, such as guaranteed values. This increases the reliability of achieving a specified design capacity.
Moreover, specifications may also contain relevant inspection requirements, that
are typically agreed upon between the purchaser of the FRP component and the
supplier as part of the purchase order or contract.
7.1.3 Compatibility and Interchangeability
In many cases, and especially in the building environment, building solutions
need to be compatible with existing systems or interchangeable with similar
components. Specifications help ensure that the selected FRP pultruded composite
will work effectively with other parts, interfaces, or systems. In essence specifications standardize how FRP composites are used for different applications and
components. This is particularly important in structural shapes since typically
during the design stage of a construction project the manufacturer is not selected,
hence designers and engineers need to assume certain aspects of the FRP composites to be used, such as geometries and mechanical properties to properly and safely
create a design for a given project.
7.1.4 Design Process
Specifications facilitate the design process by standardizing many of these
design related aspects. To this end, specifications support the implementation of
FRP components at an early design stage, making it practical for designers and
engineers to select design ‘inputs’ allowing them to make informed decisions prior
to the selection of a specific FRP manufacturer. More importantly in construction
projects, since typically the contractor is the stakeholder that selects the provider
of the FRP pultruded components, the designer will use and reference applicable
80
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
specifications to communicate with all other stakeholders in the construction value
chain - including the contractor - to ensure that the design assumptions are met.
7.1.5 Manufacturing and Process Optimization
Specifications also support the manufacturer of FRP components, by specifying
the material or component mechanical properties, composition, and tolerances. By
following these specifications, manufacturers can optimize their processes, reduce
waste, and achieve consistent product quality. As part of the specifications, manufacturers can also consider cost. By clearly defining the required properties and
characteristics of a material and component performance, manufacturers can identify alternatives or optimize the selection to balance performance requirements
with cost-effectiveness. Moreover, it can also serve as a benchmark for manufacturers to exceed minimum performance specifications, resulting in higher quality
and more advanced composite solutions compared to traditional materials, further
promoting the use of FRP components in built infrastructure.
7.1.6 Regulatory Compliance
Different industries are subject to specific regulations and standards governing
the use of FRP pultruded composites. Specifications help ensure compliance with
these regulations, whether they pertain to environmental considerations, health and
safety standards, or final product certifications. Also, specifications facilitate dealings between the purchaser and the supplier. To achieve this goal, specifications
include sufficient requirements to ensure that all batches, lots, or deliveries from
any FRP component seller conform to the specification and meet the purchaser’s
satisfaction. Moreover, in addition to material and component performance requirements, specifications will typically reference or include language that standardizes
and sets a common ‘language’ including key words, standard test methods, practices, guides, classifications, and terminologies.
7.2 CONTENT OF A STANDARD SPECIFCIATION
Specifications may have three overarching functions and, where in many cases
specifications serve all three, which include: i) Purchasing: facilitate dealings
between the purchaser and the supplier; ii) Standardization: where a deliberate
selection from the multiplicity of qualities, sizes, compositions is provided to
ultimately facilitate the implementation and design process; and iii) Providing
technical data, this will include the specific requirements that the FRP composites
material and product, must meet to be compliant with the specification.
The contents of a specification document will vary in scope based on the type of
FRP pultruded application and industry. To this end, below is a list of commonly
included content in a specification, along with brief descriptions to familiarize the
reader with the structure and expectations of a specification. Additional content
of a specification may be found to cover specific needs based on the type of FRP
application and industry.
 Title: Typically, these are concise and complete enough to identify the material, product, system, or service covered by the specification.
 Designation: Typically, a unique alpha-numerical identification, this is used
as referenced purposes in design, and contractual agreements.
 Scope: This is a critical section of many specifications, as it provides the
information and intent relating to the purpose of the specification. It concisely
states the materials, products, systems, or services to which the specification
applies and any known limitations.
 Referenced Documents: all relevant supporting documents (test methods,
terminology, practices, other specifications…etc.) are listed and included to
ensure completeness of the specification requirements.
 Terminology: All significant terms that may have a meaning more specialized
than the commonly used language are typically defined or referenced within
a specification. This provides a common language, facilitating understanding
and implementation by all stakeholders using FRP pultruded composites.
7. FRP PULTRUDED SPECIFICATIONS 81












Classification: This section may distinguish where applicable the type,
grade, and class, of FRP pultruded components used as well as the method of
designation.
Ordering Information: When a specification covers purchase options such as
different types, grades, classes, sizes…etc., it also provides standardization
information for purchase orders, simplifying the process for all stakeholders.
Materials and Manufacture: General requirements regarding the materials and
method of manufacture, i.e. pultrusion, used to comply with the specification
are included as this provides helpful information to the user of the specification and all other stakeholders.
Chemical Composition: When necessary, detailed requirements for the chemical composition and other chemical characteristics for the FRP constitute
materials, such as the fiber or resin, as well as product (e.g. in coatings), are
specified.
Properties: Generally physical, mechanical, and durability properties form
part of FRP pultruded composites specifications. Physical requirements may
include electrical, thermal, geometrical…etc. properties. Mechanical requirements may include tensile/compressive strength, tortional properties, elongation, shear strength, bond strength…etc. Durability requirements may include
moisture resistance, resistance to exposure to a diverse set of application
specific environments (acidity, alkalinity, fire…etc.).
Performance Requirements: This section will provide FRP pultruded functional, environmental, and similar requirements as necessary based on the
application and industry.
Other Requirements: Other sections in a specification may include requirements related to dimensions, mass, permissible variations, workmanship,
finish, appearance (including type, general appearance, color, and uniform
quality), and whether the FRP component is clean, sound, free of scale, and
defects.
Sampling: When the specification applies to a unit of product or material from
which specimens are to be taken for testing, the procedure for obtaining these
specimens is provided. If the specification pertains to the mean of a production lot, or bulk material, the procedure for sampling the lot or the formation
of sample test units is also specified.
Number of Tests and Retests: This section states the minimum number of
test units (test repetitions) and the number of test specimens or subunits that
are required to determine conformance to the specification. If a specification
includes retesting (where the material or product fails to pass the specification), the rules for the retesting and the conditions under which the retesting
can be permitted are provided.
Specimen Preparation: Typically, the reference test method will include
specimen preparation requirements. If special preparation is needed, such as
extracting a test specimen from an FRP component, standard specimen preparation information is provided to ensure consistency.
Test Methods: All FRP specifications will include a list of standard test
methods to complete all the requirements of a specification. When alternative procedures are given in test methods, a specification may state which
particular procedure shall be used as the basis for the specification requirement. When there is no standard test method specified for a particular quality
or property of a specified FRP material or component, a specification may
include a description of the test procedure to be followed in detail with the
specification.
Inspection: Specifications typically include technical requirements for inspections related to the delivery or installation of the FRP component. These
inspection requirements are generally agreed upon between the purchaser and
the supplier as part of the purchase order or contract.
82
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES









Rejection and Rehearing: When an FRP material or component fails to conform
to the requirements of a specification, this results in rejection of the material or
component. When this happens, rejection of the FRP material or component
occurs and is reported to the producer or supplier promptly. If there is dissatisfaction with the rejection based on the results of the test, the producer or
supplier may make a claim for a rehearing to reevaluate the rejection.
Certification: This section may be included in specifications where typically
the certification of the FRP material or component is provided by an independent third-party indicating conformance to the requirements of the specification. Such a requirement is typically specified in the purchase order or
contract, since it is established as a design requirement. Hence the purchaser
needs to furnish certification stating that samples representing each lot have
been tested and inspected as indicated in the specification and that the requirements have been met.
Product Marking: Most specifications specify the information to be marked on
the material or component, included on the package, or provided on a label or
tag. Such information typically includes the name, brand, or trademark of the
manufacturer, quantity, size, weight, specification designation, or any other
information that may be desired for a specific material or component, thus
facilitating the identification and use in a construction project.
Packaging and Package Marking: When it is desirable to package, box, crate,
wrap, or otherwise protect the FRP composite material or component during
shipment, or specify storage needs (which may adhere to a standard practice),
it’s important to include these requirements in the specification.
Keywords: Words, terms, or phrases that best represent the technical information presented in a specification are typically referenced as keywords. These
keywords are typically used as part of index and thus helps in the identification of specifications for given FRP pultruded composites applications.
Supplementary Requirements: Some specifications include supplementary
requirements, which usually apply only when specified by the purchaser in the
purchase order or contract and may be project specific.
Qualification: Qualification testing (as distinct from acceptance testing) may
be included in specifications with an identified accept/reject criteria to accept
the FRP pultruded component as a product qualification. Qualification may
refer to either a manufacturer’s periodic self-certification, a periodic submission of test results, or a complete retest of the product. Qualification requirements may include quality assurance requirements too.
Annexes and Appendixes: Additional information that needs to be included in
a specification is typically found in one or more annexes or appendixes. This
may range from detailed information such as that on apparatus or materials
that is a mandatory part of the specification but too lengthy for inclusion in
the main text. Additional information for general use and guidance, but which
does not constitute a mandatory part of the specification may also be included.
References: Specifications may include references to publications supporting
or providing needed supplementary information based on the specific application and criteria stated within the specification. Typically, historical and
acknowledgment references are included.
7.3 FRP PULTRUDED SPECIFICATIONS
Numerous types of specifications are currently published for various industry
applications and types of components related to FRP pultruded composites. Annex
D provides a detailed list of relevant specifications that are used as part of the
implementation of FRP pultruded composites, as discussed in this chapter. While
the list provided is extensive, there are FRP pultruded specification gaps, which is
addressed in the next section of this Chapter. The specifications can be classified
in the following groups:
7. FRP PULTRUDED SPECIFICATIONS 83
7.3.1 Design Specifications
A design specification is a type of specification document that specifies the
design requirements and includes a list of criteria that an FRP composite needs to
address. These criteria may extend beyond physical, mechanical, and durability
properties and include aesthetics, function, and other specifications. This type of
specification may be product, project, or application specific. It may be part of a
design guide or code, where detailed information on FRP pultruded components
design related aspects are provided in the next chapter of this document.
7.3.2 Material Specifications
These types of specifications are comprised of standard test methods relevant to
the constituent materials that form part of the FRP pultruded component, or used as
part of the application of FRP components (for example in adhesive applications,
as discussed in the next Chapter of this document). Such specifications include the
tests for the different applicable physio-mechanical, chemical, and other properties for raw materials used in the manufacturing of pultruded FRP components.
These specifications may be used by manufacturers as means to establish supplier
requirements. Also, these specifications can be referenced by design guides to
define specific materials to be used for relevant applications.
Prominent material specifications in FRP pultruded applications includes fiber
specifications. Most notably are for example ASTM D578, “Specification for Glass
Fiber Strands” which establishes the requirements for glass fiber used on FRP products, and the more recently published ASTM D8448, “Specification for Basalt Fiber
Strands” providing the requirements for basalt fiber used in FRP products. Other
material standard specifications may be developed and provided by fiber or resin
manufacturers, which will include all relevant raw material specific requirements.
Similarly, many resin based specifications are typically developed and provided by
resin manufacturers due to the wide range of performance requirements that can be
obtained from different resin formulations. Some standard resin based specification
examples include: ISO 3673–1, “Plastics—Epoxy Resins—Part 1,” ASTM D1763,
“Standard Specification for Epoxy Resins,” ASTM D1755, “Standard Specification for Poly(Vinyl Chloride) Resins,” ASTM D4690 “Standard Specification for
Urea-Formaldehyde Resin Adhesives.”
Overall, the objective of material-based specifications is to set the necessary
requirements of FRP pultruded constituents, including referencing the testing standards used to evaluate the different properties.
7.3.3 FRP Component Specifications
These types of specifications, while relatively limited, define the minimum
requirements of a specific FRP pultruded component. Typically, these specifications will reference testing and specific performance-based requirements for a
given FRP component used in a specific application, or a specific parameter for
FRP components, some examples include: ASTM F3059, “Standard Specification
for Fiber-Reinforced Polymer (FRP) Gratings Used in Marine Construction and
Shipbuilding,” ASTM D3917, “Standard Specification for Dimensional Tolerance
of Thermosetting Glass-Reinforced Plastic Pultruded Shapes,” ASTM D8505,
“Standard Specification for Basalt and Glass Fiber Reinforced Polymer (FRP) Bars
for Concrete Reinforcement.”
These specifications aim to ensure a level of quality to be accepted in a specific
FRP application, and in essence set the acceptance criteria for the use of the FRP
component. To this end, these specifications may encompass various requirements,
extending beyond physical, mechanical, and durability aspects to include application-specific needs.
7.3.4 Project / Construction Specifications
Since FRP pultruded components are a relatively novel material solution in the
built infrastructure, there is a limited development of well-established standard
specifications that covers the numerous and varied types of applications and needs
84
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
of the construction industry. To fill this gap, project and construction specifications
are typically developed by the different stakeholders (owner, developer, architect,
engineer, contractor…etc.) to specify the requirements for that specific project.
Whenever possible, these specifications will include other specifications, typically
referencing test standards as well as other project and construction specifications.
In many cases, the FRP manufacturer will support the development of this type of
specification, to ensure that any requirements (performance, geometry…etc.) can
be met within current solutions. Hence engaging a manufacturer or expert with
knowledge early on in a project where FRP composites are expected to be used is
important to ensure that rational and valid specifications are provided.
It is important to clarify that there are several full scale FRP component test
methods, as discussed in the previous Chapter, where these test methods typically
apply to the FRP component for a given application (e.g. ASTM D8019, “Standard
Test Methods for Determining the Full Section Flexural Modulus and Bending
Strength of Fiber Reinforced Polymer Crossarms Assembled with Center Mount
Brackets”). The test method will only provide the method to test, not the performance requirements. Hence a project or construction specification will reference
such test methods and include the applicable performance requirements for that
specific project. Moreover, it is not uncommon to see project or construction specifications that reference generic or non-FRP specific test methods as part of the
requirements for testing, such as in the ASTM D1036, “Standard Test Methods of
Static Tests of Wood Poles,” which is a test method for to wood piles is generally
used in project specifications for FRP utility poles.
7.3.5 Quality Control Specifications
These types of specifications will typically be developed by FRP manufactures,
and required by agencies that approve the use of FRP products (product approval
protocols). The main difference to the other specifications referenced before, is
that in addition to the FRP performance requirements (physical, mechanical and
durability …etc.) quality control (QC) and quality assurance (QA) based specifications will embrace continuous improvement by analyzing quality control data,
customer feedback, and internal processes. As such a quality system is developed
and implemented where corrective and preventive actions are taken based on identified issues or opportunities for enhancement. To achieve this, the quality system
implements a system to maintain accurate documentation and traceability of all
relevant processes to manufacture the FRP pultruded composites. This includes
recording information such as material suppliers, batch numbers, manufacturing
processes, test results, and inspection records. Traceability is crucial for identifying any issues and ensuring product consistency.
A QC/QA specification will also define the acceptance criteria for the composite
material and component based on the required performance and regulatory standards. Establish acceptable tolerance ranges for mechanical properties, dimensional
specifications, and any other relevant parameters. This ensures that the composite
material meets the desired quality standards before it leaves the factory. Additionally, statistical process control techniques may be implemented to monitor and
analyze process data over time. This helps identify any trends, variations, or outof-control conditions in the manufacturing process of FRP pultruded components.
By implementing quality control specifications, it ensures that the FRP pultruded
composite materials and products consistently meet the required standards, performance criteria, and customer expectations.
7.4 GAPS IN FRP PULTRUDED SPECIFICATIONS
Addressing potential specification gaps as described herein, will help ensure
that FRP pultruded materials and components, selected and manufactured meet
the required performance, durability, and quality standards for the specific applications. Moreover, addressing these gaps will further the implementation of FRP
composites in infrastructure applications. It is important to engage with experts in
7. FRP PULTRUDED SPECIFICATIONS 85
the field and leverage industry standards and guidelines to develop comprehensive
and effective specifications. Two main specification gaps are described below:
7.4.1 Application Specifications
One common gap is the absence of detailed performance requirements specific
to the FRP pultruded application. In many cases, either no specification is available, or a non-FRP specification is used as an alternative that does not address or
apply to FRP materials, limiting the advantages and benefits provided by pultruded
composites. The specification may not clearly define the desired mechanical properties, such as tensile strength, flexural strength, or impact resistance, needed for
the FRP material. This can lead to ambiguity and result in suboptimal material
selection.
To address this gap, it is important to develop FRP specific application specifications that thoroughly analyze the application and identify the critical performance requirements for the given application. This can be done by considering
the anticipated loading conditions, environmental exposure, and relevant available
industry standards or regulations. In many cases, the necessary supporting studies
and information is already available to develop such specifications. Development
of such specifications with the desired performance characteristics is critically
needed, setting appropriate targets or acceptance criteria for the FRP materials and
FRP application to further the implementation of FRPs.
7.4.2 Long Term Performance
FRP materials can be susceptible to degradation over time due to environmental
exposure, such as ultraviolet (UV) radiation, moisture, or chemical exposure. To
date, some specifications may not adequately address the long-term durability
requirements of FRP materials.
As of today, there is no unified method to quantify and assess the durability
of FRP pultruded components. Given the limited number of FRP structures that
have been in use for over a decade, there is scarce field evidence of the long-term
durability of these components. While there have been many studies evaluating the
long-term performance of FRP composites in different applications and outside of
construction (marine, wind energy…etc.), there are still concerns on the durability
of FRP composites within the field of construction, since minimum design life of
these structures is 50 years.
Substantial work based on laboratory aging of FRP composites using accelerated
conditioning protocols has been published (aimed to predict the long-term durability of FRP pultruded components in real-life). In these studies, various accelerating conditioning methods, such as high temperature and aggressive conditioning
solutions, are used to simulate the deterioration that occurs in real conditions.
Specifications need to leverage the available knowledge that has been developed
by adequately referencing and standardizing durability specification requirements
for FRP composites based on the different applications.
Another specification long term performance gap is that related to UV radiation.
This degradation mechanism is linked to the types of resins where the first FRP
applications suffered greatly from UV. Nevertheless, today resins, coatings, and
manufacturing solutions are specified and formulated specifically to provide UV
protection. However, no industry-wide accepted specification exists to determine
the UV resistance of FRP pultruded composites.
7.4.3 Fire Performance
The lack of standardized fire performance testing for FRP pultruded elements
is a significant gap in the industry. Without unified testing protocols, assessing
the fire performance of FRP pultruded components becomes inconsistent and may
lead to safety concerns.
Developing comprehensive standards for fire performance testing is essential to
validate the performance of these materials under fire different conditions. Such
standards would build confidence in their use in construction, ensure compli-
86
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
ance with safety regulations, and facilitate the broader adoption of FRP pultruded
elements in various applications. Addressing this gap is crucial for the continued
growth and innovation in the field.
7.4.4 Unification of Standards
The absence of unified standards across different aspects of FRP pultruded materials, including mechanical properties, durability, and fire performance testing,
creates challenges in ensuring consistent quality and performance. Disparate standards can lead to confusion, hinder compliance, and limit the potential advantages
of FRP materials. Establishing unified standards that are accepted industry-wide is
a critical need. Such unification would promote best practices, streamline compliance processes, foster innovation, and enhance collaboration among stakeholders.
The development and adoption of unified standards that homogenize requirements,
would be a significant step toward realizing the full potential of FRP pultruded
materials in modern construction.
8. FRP DESIGN: GUIDELINES & JOINTS 87
8. FRP DESIGN: GUIDELINES & JOINTS
8.1 DESIGN STANDARDS
Design standards and guides are the first crucial document for full adoption of
any type of material system or solution in the built infrastructure. This is especially true for non-traditional materials such as FRP composites, as guides provide
engineers and designers with standardization, safety and reliability information,
regulatory compliance information, efficiency of design, and usually are the fundamental documents for collaboration between the many stakeholders involved in a
construction project.
The advancement of design of FRP pultruded elements used in built structures has reached a level of maturity [39]. This section provides a comprehensive
description of available design guides for the use of FRP pultruded elements that
can be adopted by engineers, architects, and designers; enabling them to incorporate FRP pultruded composites into their projects effectively. The design guides
presented herein are well established guides that have been peer reviewed and
developed based on published scientific research, offering valuable insights into
the various aspects of FRP structures, including material selection, analysis techniques, and construction practices. They outline the best practices and recommendations for designing FRP structures to ensure optimal performance, safety,
and durability. These guides typically cover load calculations, design methodologies, connection details, and quality control measures specific to FRP material
and ultimately serve as a mechanism to transfer knowledge and education for the
design of FRP composites. By following these design guidelines, professionals can
harness the full potential of FRP composites, taking advantage of their exceptional
strength, lightweight nature, corrosion resistance, and flexibility. Ultimately, the
design guides provide the first step in facilitating the widespread adoption of FRP
structures in diverse applications, ranging from bridges, buildings to waterfront,
transportation, utility, and telecommunication structures.
8.1.1 Codes and FRP Composites
Prior to introducing and describing the specific design standard documents that
are currently available for the design of FRP pultruded elements, it is necessary
to state the obvious; ‘plastics’ and FRP materials have been part of the I-codes, or
international building code (IBC) for several decades (IBC 2000).
Specifically, ‘plastics’ have been approved materials as part of the IBC Chapter
26 as any thermoplastic, thermosetting or reinforced thermosetting plastic material, where typically the requirements have been conformance to combustibility
classifications specified in the relevant building code sections. In fact, the IBC
(IBC 2023) uses the following definitions:
i.
Plastic, Approved: A polymeric composite material consisting of reinforcement fibers, such as glass, impregnated with a fiber-binding polymer which
is then molded and hardened. Fiber-reinforced polymers are permitted to
contain cores laminated between fiber-reinforced polymer facings.
ii.
Thermoplastic Material. A plastic material that is capable of being repeatedly softened by an increase in temperature and hardened by a decrease in
temperature.
iii.
Thermosetting Material: A plastic material that is capable of being changed
into a substantially nonreformable product when cured.
Moreover, FRPs have been explicitly part of the building code, where Section
2613 of the IBS (IBC 2023) includes the provisions for the use of fiber-reinforced
polymer in and on buildings and structures. Fiber Reinforced Polymer is defined
within the IBC as ‘A polymeric composite material consisting of reinforcement
fibers, such as glass, impregnated with a fiber-binding polymer which is then
molded and hardened. Fiber-reinforced polymers are permitted to contain cores
laminated between fiber-reinforced polymer facings.’
88
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Hence, all stakeholders involved in construction projects using FRP pultruded
components can feel more comfortable embracing these materials, which are not
‘innovative’ and can offer significant advantages to their projects. FRP pultruded
components enable architects, engineers, owners, and stakeholders to re-think
construction and the value of building with nonmetallic materials. As previously
states, FRPs enable longer service life of structures, lower maintenance costs, as
well as faster construction, amongst other attributes.
8.1.2 ASCE/SEI 74
For over a quarter of a century, the development of a design standard for
pultruded ‘fiber-reinforced-plastic’ structures by the American Society of Civil
Engineers (ASCE) in collaboration with the Pultrusion Industry Council (PIC) of
the Society of Plastics Industry (SPI), has been underway (Chambers 1997). While
a comprehensive outline of a ‘pre-standard’ guide was developed, with significant
amounts of research undertaken to develop the design models for FRP pultruded
components; it was not until November 9, 2010, when the ASCE ‘Pre-Standard
for Load & Resistance Factor Design (LRFD) of Pultruded Fiber Reinforced
Polymer (FRP) Structures’ was published by ASCE and submitted to the American
Composite Manufacture Association (ACMA). While the pre-standard has been
used as a guiding design document in FRP pultruded projects until now, its use
has been limited since a ‘Pre-Standard’ does not represent something mandatory
nor provides assurance of standardization in which designers, engineers, and other
stakeholders in FRP pultruded construction projects can depend on.
More than a decade since the publication of the Pre-Standard, it was recently
announced during the 2023 North American Pultrusion Conference (NAPC) in
Chicago, Illinois, by ACMA, that after numerous ballots, hundreds of negative
comments, and resolution of comments, the American Society of Civil Engineers
and Structural Engineering Institute, ASCE/SEI-74 ‘LRFD for Pultruded FRP
Structures’ was approved to be published. This is a milestone in the history of FRP
pultruded elements. The new design document is expected to be published in the
coming months, upon the implementation all editorial comments.
This new load and resistance factor design (LRFD) based standard is derived
from the Pre-Standard (ASCE 2010) [40] and consists of nine mandatory chapters
containing obligatory criteria and an additional nine chapters of commentary that
are non-mandatory, along with two supplementary chapters dedicated to a glossary
and symbols. These chapters encompass various topics, including:
i.
General Provisions: Including reference specifications, materials, design
basis, loads and load combinations, structural design drawings and specifications, as well as fabrication, construction, and quality assurance
requirements.
ii.
Design Requirements: Including property of sections, design strength,
nominal strength and stiffness, stability of frames and members, design
for serviceability, ponding, fatigue, connections, and gross and net areas
requirements.
iii.
Design of Tension Members: Including general provisions, nominal axial
tensile strength, slenderness limitation, and built-up members requirements.
iv.
Design of Compression Members: Including general provisions, slenderness, and effective length considerations, factored critical strength in
compression of common sections, compression strength for members
with other cross-sections, and compression strength for built-up members
requirements.
v.
Design of Members for Flexure and Shear: Including design basis for
flexure and shear (factored nominal strength of members due to material
rupture and/or buckling), design for concentrated forces, and design for
copes, notches, holes, and openings.
vi.
Design of Members Subjected to Combined Forces and Torsion: Including
general design requirements, doubly and singly symmetric members
8. FRP DESIGN: GUIDELINES & JOINTS 89
subject to flexure and axial forces and torsion and combined torsion and
flexure, and/or axial force requirements.
vii.
Design of Plates and Built-Up Members: Including general provisions,
design of plates subject to flexure, or through-the-thickness shear, or in
plane tensile loading, or compressive loading, or in-plane shear loading, as
well as design of built-up members and serviceability requirements.
viii. Design of Bolted Connections: Including general provisions, connection design for single, two or three row bolted connections, simple frame
connections, as well as column bases and bearing on concrete connection
requirements.
ix.
Seismic Design Requirements: Including design of seismic loads in category
A, design parameters and limitations for seismic force-resisting systems in
categories B through F, design for elements not part of the seismic forceresisting system, and seismic force-resisting system requirements.
In summary, the new ASCE/SEI 74-23 [41] is a comprehensive load and resistance factor design standard for FRP pultruded structures that provide the missing
assurance for all stakeholders in projects involving FRP, ensuring safety and reliability. This standard provides a turning point for FRP pultruded elements in the
USA as designers, engineers, and owners can reliably reference the standard for
construction projects using FRP pultruded components. In other words, the forthcoming ASCE/SEI 74-23 guide provides the foundation for the widespread use of
FRP pultruded applications.
8.1.3 CEN/TC prEN 19101
In 2010, the European Commission created the Technical Committee 250 (TC
250) to revise all Eurocodes in a 10-year project, tentatively ending in 2020.
Working groups were also formed to address the inclusion of other materials into
the Eurocodes. Among these groups, the Working Group 4 (CEN/TC 250/WG
4) was responsible for the development of design standards for FRP materials.
Under this initiative, in 2016 a technical report titled ‘Prospect for new guidance
in the design of FRP’ was published (EC 2016), introducing the policy framework
and the CEN/TC250 initiative and well as the prospect for CEN guidance for the
design and verification of composite structures designed with FRP composites.
Since then, in 2022, a pre-standard was published pr EN/TS 19101 [42], ‘Design
of fiber-polymer composite structures’ (EN 2022). As a technical specification
(TS) it provides the principles and requirements for the safety, serviceability, fire
resistance and durability of structures, including their design and verification that
are given in the European Standards under EN 1990. The underlying methodology
is based on probabilistic design as the basis of structural design in the Eurocodes.
As such the document provides tables with derived values for different factors
such as material partial factors, conversion factors…etc. This document provides
engineers and designers with a set of regulations and procedures to ensure FRP
composite’s structural integrity and performance meets European standards. It
comprises twelve clauses, including provisions such as basis of design, durability,
and fatigue, among others. Additionally, it includes five annexes covering topics
like creep coefficients, buckling of orthotropic laminates and profiles, bridge
details, and more asw follows:
i.
Scope: The TS that applies to the design of buildings, bridges and other
civil engineering structures in ‘fiber-polymer’ composite materials using
glass, carbon, basalt, or aramid fibers, with a matrix based on unsaturated
polyester, vinyl ester, epoxy, or phenolic thermoset resins. It includes
permanent, temporary, and all-composite, and all-hybrid structures; the
values of material temperature in structural members, joints, and components in service conditions are (i) higher than -40 °C and (ii) lower than
- 20 °C.
This TS standard does not cover FRP composite components used for
internal reinforcement of concrete structures (FRP composite rebars) or
90
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
strengthening of existing structures (composite rebars, strips or sheets),
cable-stayed structures honeycomb cores, or composites made from
natural fibers and/or thermoplastic resins. Additionally, specific requirements concerning seismic design are not considered in the document.
Other requirements, e.g., concerning thermal or acoustic insulation, are not
considered.
ii.
Normative References: Includes a list to the applicable European normative
references such as: EN 1990, EN 1991, EN 1993, EN 1997, EN 1998 and
other FRP pultruded profiles relevant specifications.
iii.
Terms, Definitions and Symbols: Including terms, definitions, symbols, and
symbols for member axes.
iv.
Basis of design: Including general rules, principles of limit state design,
basic variables, verification by the partial factor method, and design
assisted by testing specifications.
v.
Materials: defines the materials allowed to use including limits in glass transition temperature limitations, core material and adhesives specifications.
vi.
Durability: Includes general considerations, environmental conditions,
effects and measures for specific environmental conditions, and combined
conditions, and durability measures for connections and joints.
vii.
Structural Analysis: Includes modelling analysis, global analysis, consideration for imperfections and method of analysis.
viii. Ultimate Limit States: Including the general considerations and ultimate
limit state of laminates, profiles, and sandwich panels.
ix.
Serviceability Limit States: Including general considerations, deflection,
vibrations, and matrix cracking specifications.
x.
Fatigue: Including general considerations, as well as fatigue actions, verification, and testing.
xi.
Detailing: Including general considerations, detailing for profiles, sandwich panels, bolted connections, and adhesive connections.
xii.
Connections and Joints: Including general rules bolted and adhesive
connections, and joints as well as hybrid connections and joints.
The annexes cover the following technical specifications relevant to the design
of FRP elements:
i.
Creep Coefficients: This includes the inclusion of creep-relevant coefficients for pultruded composite profiles, laminates, and core materials.
ii.
Indicative Values of Material Properties for Preliminary Design: Including
general considerations, and the application of different fibers, resins, core
materials, ply properties and laminate properties.
iii.
Buckling of Orthotropic Laminates and Profiles: Including general considerations, and elastic buckling of orthotropic laminates and profiles.
iv.
Structural Fire Design: This includes general considerations and assumptions, the basis of design, material properties, tabulated design data, and
both simplified and advanced design methods.
v.
Bridge Details: This includes general considerations, bridge bearings,
expansion joints, parapets, adhesive deck-girder connections, and crash
barrier fixations.
It is important to mention that CEN/TS 19101 had a 13th chapter that was eliminated during the development of the document titled: ‘Production, installation
and maintenance.’ This chapter included mandatory language relevant to general
considerations, quality management aspects, design quality, execution quality of
the FRP pultruded elements and maintenance. This provides insight to an area
that will need to be addressed in other means, and such aspects are critical to the
success of FRP pultruded composites in the built infrastructure.
While design standards or technical specifications are the first step towards full
implementation for FRP pultruded elements, providing supporting documents
(such as a design manual of worked examples) that guide on critical design aspects
with practical design information for the design engineer, are common part of the
process. To this end, in addition the technical specification, a valuable resource
8. FRP DESIGN: GUIDELINES & JOINTS 91
to assist designers in implementing CEN/TS 19101 has been developed. This is
a commentary document, consisting of 396 individual background reports spanning approximately 1000 pages, providing detailed explanations and insights into
the standard’s provisions, with the necessary scientific reference to support the
rationale and development of the technical specification (CEN 2021). A second
resource that is underway, is composed of a collection of worked examples,
offering engineers and designers practical illustrations and solutions for applying
CEN/TS 19101 to various structural elements. These supplementary documents
serve as valuable references, aiding professionals in effectively incorporating the
Eurocode standard into their design processes using FRP pultruded elements.
8.1.4 Manufactures’ Design Manual
Besides standards or guides developed by institution, national, or international
standard developing organizations; many FRP manufacturers develop internal/
external design guides which is a resource that has existed since the beginning
of pultruded composites. While many of this these standards, guides or design
manuals are typically limited to the products produced by the manufacturer and
thus product specific, they provide a helpful resource for any stakeholder to obtain
fundamental design-based information to consider FRP pultruded composites as a
built infrastructure solution.
These design guides typically precede many of the established pre-standards,
and get revised on an as needed basis, providing a valuable resource for engineers and designers working with pultruded FRP materials. Manufacturers’ design
guides provide specific information, limitations, and recommendations related to
their products, processes, and capabilities. Typically guides or manuals outline the
design principles, methodologies, and guidelines for designing the structures and
components using the manufacturers’ fabricated pultruded profiles and systems.
These guides are provided either online, electronically or in traditional paper form
and typically include practical information in a tabulated form, with relevant material properties, load capacities, deformation limits, and performance characteristics. Some examples of these readily available design manuals, guides and standards are listed below, with many others available:
i.
The Pultex® pultrusion design manual, by Creative Pultrusions.
ii.
Design Manual, by Strongwell
iii.
Design guide, by Bedford.
iv.
Fiberglass grating and structural products design manual, by AIMS
International.
v.
Dynaform® FRP Structural Shapes Design Guide, by Fibergrate Composites Structures.
vi.
Design guide, by Wagners.
Overall manufacturer-based design guides offer design considerations and
guidelines for various standard applications, such as structural beams, columns,
panels, gratings, and other custom components. They may provide load tables,
design equations, and practical examples to assist engineers in determining appropriate sizes, configurations, and connection details for their specific projects. These
manufacturer-specific design guides are valuable resources as they are tailored to
the unique characteristics and capabilities of the pultrusion products each manufacturer offers. They help ensure that engineers and designers can optimize their FRP
designs’ performance, adequately select products, providing necessary detailing,
while ensuring structural integrity utilizing the manufacturer’s specific pultruded
profiles and systems.
8.1.5 Other Design Resources
In addition to the design standards and manuals mentioned earlier, due to the
long-established history, development, and use of FRP pultruded elements across
various industries (as discussed in Chapter 2), there is a wide range of other designbased resources available to assist designers and engineers when implementing
FRP pultruded components.
92
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
These other resources will range from general to very specific design problems,
from overview of design methodology to specific design constraints, or the design
document may be FRP element specific (e.g. connection or column), or application specific (e.g. bridges). These other resources vary widely in form and some
examples include:
i.
Books developed by experts and published by different publishers.
ii.
Guidelines and recommended practices published by societies or associations (such as ASCE or ACMA), or national agencies such as the National
Institute of Standards and Technology (NIST), or federal Department of
Transportations (DOTs).
iii.
Technical white papers prepared and provided by manufacturers, or institutions or other research organizations.
iv.
Peer reviewed work, published by an array of journals with focus in either/
or built infrastructure, pultrusion, composite materials…etc. These types of
resources tend to tackle specific design issues.
8.2 DESIGN PHILOSOPHY
The two principal design philosophies used with FRP pultruded structural
members are: i) Allowable Stress Design (ASD), which is based on the Structural
Plastics Design Manual by ASCE (ASCE 1984) [2], and ii) Load and Resistance
Factor Design (LRFD). While both the ASCE/SEI 74-23 and CEN/TC prEN 19101
design standards are based on LRFD philosophy, ASD is still widely used for FRP
structural members because it is a simple design methodology and because of
the linear stress–strain responses of FRP elements. The design philosophies are
presented, recognizing the advantages and limitations each one provides in association with current FRP manufacturing procedures and design standards.
8.2.1 Allowable Stress Design (ASD)
Fundamentally, ASD is a design methodology used in structural engineering to
determine the maximum allowable stress that a material or structural component
can sustain under various load conditions. In ASD, the design loads (such as dead
loads, live loads, wind loads… etc.) are determined based on applicable building
codes and standards. These loads are then multiplied by a factor of safety to obtain
the ultimate (or factored) loads that the structural component can carry safety. The
ultimate loads are further reduced by applying resistance factors to the material
strengths, which results in the allowable or design strengths.
The design is carried out by comparing the factored loads to the allowable
strengths. If the factored loads are lower than the allowable strengths, the design is
considered safe. However, if the factored loads exceed the allowable strengths, the
design needs to be revised to increase allowable stresses that a material or structural component (i.e., the capacity) such as increasing the section, material changes
may be required. It should be noted that ASD is typically used for designing structures made of materials like steel, timber, and aluminum, since material properties
and failure modes are well understood with relatively predictable behaviors.
Fundamentally, ASD relies on established design standards and empirical
formulas based on extensive testing and experience. It’s important to note that ASD
has certain limitations and assumptions, and may not be suitable for all types of
structures or materials due to variability and uncertainties in loadings, material
properties, and structural behaviors.
To achieve this, ASD stresses in FRP pultruded composites are limited by a
relevant failure criterion that includes an appropriate safety margin. Many design
codes define the material’s characteristic or resistance strength as the lower fifth
percentile of the test data under specific loading conditions or corresponding to a
particular failure mode. For instance, several material standard specifications (as
previously discussed) define the characteristic (or guaranteed) value as a material
property representing an 80% lower confidence bound interval on the fifth percentile of a specified population, considering the coefficient of variation (COV). A
nominal value is calculated at the five percentile using scale parameters, and the
8. FRP DESIGN: GUIDELINES & JOINTS 93
COV is determined using the Gamma function. Subsequently, the characteristic
value is obtained by further reducing the nominal value by the confidence factor.
In addition, knockdown (environmental) factors are incorporated to account for
the loss of strength or stiffness during the service life of FRP pultruded composites due to physical or chemical aging effects, moisture effects, size effects, and
sustained stresses. This is equivalent to those factors used by timber member
design codes under the National Design Specification (NDS) for Wood Construction [43]. Thus, in ASD, an allowable strength (Ra) is obtained by dividing the
nominal strength (Rn) by a safety factor (Ω), and R must be greater than or equal
to the basic load combination (Q):
Ra Ra
Q
where:
Ra = allowable strength or required strength (= Rn/Ω)
Rn = nominal strength (computed based on member’s nominal or characteristic
properties)
Ω = factor of safety (based on prior experience, see Table 5)
Q = basic load combination defined per applicable design codes.
The allowable or required strength (Ra) must be greater than the sum of stresses
induced by service loads (Q). The basic load combinations for the ASD method are
provided by ASCE/SEI 7-10 [44] and are as follows:
Load combination 1: D
Load combination 2: D + L
Load combination 3: D + (Lr or S or R)
Load combination 4: D + 0.75L + 0.75 (Lr or S or R)
Load combination 5: D ± (1.0W or 0.7E)
Load combination 6: D + (1.0W or 0.7E) +0.75L + 0.75 (Lr or S or R)
Load combination 7: 0.6D ± (1.0W or 0.7E)
For the ASD approach, the safety factors, Ω, will vary based on the type of
structural member and failure mode, and may vary slightly between manufacturers
(e.g., Bedford Reinforced Plastics, Creative Pultrusions Inc, Strongwell Corporation, Fiberline, and others), as shows in Table 5, which are then applied in the
design procedures.
8.2.2 Load and Resistance Factor Design (LRFD)
In recent years, the LRFD approach has gained more prominence in many
design codes, offering a more comprehensive and probabilistic methodology that
considers the variability and uncertainties in loadings, material properties, and
structural behaviors. In principle, LRFD is used to determine the required strength
of a structural component or system to safely resist applied loads.
LRFD considers the uncertainties in material strengths, loads, and other factors
by using load and resistance factors. The design loads, such as dead loads, live
loads, wind loads…etc., are determined based on applicable building codes and
standards. These loads are then multiplied by load factors to obtain the factored
loads, which represent the expected
maximum loads that the structure may
Table 5 - Safety Factors for Allowable Stress Design (ASD)
experience during its lifetime. Then,
Members
Strength
Safety Factor
the design is carried out by comparing
Flexural strength
2.5–3.0
the factored loads to the design
Pultruded beam
Shear strength
2.5–3.0
strengths of the structural elements
Buckling
strength
2.5
or systems. The design strengths are
obtained by dividing the nominal or
Pultruded column
Compressive strength
3
characteristic strengths of the mateAxial tension member
Tension strength
2
rials by resistance factors, which
Joint and connection
Bearing strength
4
94
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
account for the variability and uncertainty in material properties, workmanship,
and other factors affecting the resistance to loads.
In this regard, LRFD offers a more rational and consistent basis for structural
design when compared to ASD. It considers the probabilities of load exceedance
and resistance variability, resulting in a higher level of reliability and safety in
design. The load and resistance factors (discussed below) used in LRFD are determined based on statistical analyses, research studies, and calibration with actual
structural performance data. They are typically provided in design codes and standards specific to each material and structural type. Using an acceptable probability
of failure approach, FRP composite members are designed to withstand single or
multiple loadings, such as bending, shear, and combinations, that may occur during
the structure’s service life. The LRFD design objective focuses on several key
factors, primarily:
i
Strength: Determined based on short-term tests conducted on new materials.
ii.
Durability: Accounts for design properties, such as strength and modulus,
in the end-use condition. Durability is obtained by testing the retained
properties after exposure to the expected environment for the entire life
duration.
iii.
Reliability: Considers the variability of loads and resistance, which affects
the reliability of the structure or the probability of failure. This consideration is on par with other construction materials. The design also considers
any biases in the formulas used to predict failure in relation to test results
for specific failure modes.
iv.
Time effects: Addresses the creep and creep rupture of the material when
subjected to sustained loads over an extended period.
In general, LRFD considered two main limit states for design: a) serviceability
limit state that includes the instantaneous and long-term serviceability of pultruded
FRP members controlled by material and structural degradation, vibration and
defection, rotation, human response, etc.; and b) ultimate limit state relates to the
structural life safety controlled by the strength of the FRP composite, its stability,
failures, and collapse of both the structural component and system. By the acceptable probability of failure approach, FRP composite members are designed to
sustain single or multiple loadings. The load factors provided in ASCE 7 (ASCE
2010) are based on a 50-year service life of a structure. Pultruded FRP members
under LRFD are designed so that their design strength equals or exceeds the
required strength (the effects of the factored loads) in the basic load combinations
as follows:
Load combination 1:
1.4D
Load combination 2:
1.2D + 1.6L + 0.5 (Lr or S or R)
Load combination 3:
1.2D + 1.6 (Lr or S or R) + (0.5L or 0.8W)
Load combination 4:
1.2D + 1.0W + 0.5L + 0.5 (Lr or S or R)
Load combination 5:
1.2D +1.0E + 0.5L + 0.2S
Load combination 6:
0.9D + 1.0W
Load combination 7:
0.9D + 1.0E
To ensure that the induced or applied load is less than the failure load of the structural element, load factors are introduced and applied to service loads. In general,
load factors are higher than unity. The sum of all service loads, including their
corresponding load factors, is called the factored load (Qu). The factored load is a
failure load greater than the total actual service load. In addition, nominal strength
(Rn) of structural members is reduced using a resistance factor (φ), as presented in
Table 6, and time effect factor (λ), as provided in Table 7. These strength reduction
factors are typically less than unity.
λφRn = Qu
Where:
Rn = nominal strength based on the reference (nominal or characteristic)
strength of the structural member (adjusted as per end use conditions)
Qu = factored load (minimum required member resistance)
8. FRP DESIGN: GUIDELINES & JOINTS 95
φ=
resistance factor (Table 6.)
λ=
time effect factor (Table 7.)
It should be noted that the LRFD design equations and load factors of the ASCE
Pre-Standard (ASCE 2010) are based primarily on glass fibers, fabrics, and mats
only. As such, limited data is available on other fiber and resin constituent materials such as basalt, carbon, or aramid FRPs. The adjustment factors are based on
end use conditions which are moisture condition, temperature variation, pH variations including times of exposure, and others. Nevertheless, based on the LRFD
approach, the design ensures that the nominal resistance of a material and statistically derived (characteristic value) resistance factor i.e., () is greater than the sum
of the products of different load factors multiplied with the corresponding load
types (factored load effect or Qu). Hence, resistance factors will correspond to
uncertainties in constituent material properties and the manufacturing processes
in addition to the accuracy of equations predicting different stresses induced in a
structure. In addition, resistance factors account for the consequences of failure.
The resistance factor (φ) is considered for uncertainties in any one or several
of structural resistances of pultruded FRP members. The uncertainties in structural resistances can be attributed to the influence of variability inherent in the
material and geometrical properties, manufacturing, environments, or others. The
resistance factor is used to reduce the predicted nominal strength of structural
members. The appropriate resistance factors provided in the Pre-Standard for
LRFD (ASCE 2010) are presented in Table 6.
The fibers in an FRP pultruded composite are assumed to behave linear elastic
to failure, but the viscoelastic properties responsible for creep behavior are typically found in pultruded FRP structural members due to the influence of matrix
(cured resin) that helps transfer loads from one fiber to another. In this regard, the
time effect factor is commonly used
to compensate for stiffness reducTable 6 - Resistance Factor (φ) Based on the Pre-Standard (ASCE-74)
tion throughout the service life of
Members
Strength
Resistance Factor φ
pultruded FRP structural members.
Rupture strength
0.65
The time effect factors for each basic
Local buckling strength
0.8
load combination based on the PrePultruded member (flexural
Global
buckling
strength
0.55
Standard (ASCE 2010) are presented
and shear)
in Table 7.
Local crippling
0.7
Ultimately, the load and resistance
Torsional strength
0.7
factors used in LRFD are determined
Flexural buckling strength
0.7
based on statistical analyses, research
Axial compression member
Local
buckling
strength
0.8
studies, and calibration with actual
structural performance data. ManufacAxial tension member
Tension rupture strength
0.65
turers play a critical role in improving
the design process and reliability of the
Table 7 – Time Effect Factor λ Based on the Pre-Standard (ASCE-74)
Basic Load Combination
Time Effect λ
Load combination 1: 1.4D
Load combination 2: 1.2D + 1.6L+0.5 (Lr or S or R)
0.4
L is from occupancy
0.8
L is from storage
0.6
L is from impact
1
Load combination 3: 1.2D + 1.6 (Lr or S or R) + (0.5L or 0.8W)
0.75
Load combination 4: 1.2D + 1.6W + 0.5L + 0.5 (Lr or S or R)
1
Load combination 5: 1.2D + 1.0E + 0.5L + 0.2S
1
Load combination 6: 0.9D + 1.6W
1
Load combination 7: 0.9D + 1.0E
1
The full design load acts during the entire service life equal to or exceeding 50 years
0.4
96
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
design factors specific to each material and structural type. It’s important to note
that LRFD requires more sophisticated calculations and consideration of multiple
load combinations when compared to ASD. It may also require more extensive
knowledge of structural behavior and material properties. However, LRFD offers
a more robust and consistent approach that accounts for the uncertainties in design
parameters, making it a preferred choice in modern structural design practices.
8.3 JOINTS & CONNECTIONS
Design standards used for FRP pultruded elements have dedicated sections to
designing joints and connections, as this represents a critical design aspect for
many FRP pultruded frame type structures. Joints are essential components that
enable the connection of different structural FRP members. Joints play a critical
role in transferring loads and maintaining the overall stability and integrity of the
structure, where the design considerations of joints in FRP pultruded elements
differ from traditional construction materials like steel due to the unique properties of FRP materials. Connecting FRP elements is necessary for many reasons,
ranging from the project geometry and configuration, physical constraints, FRP
production constraints limit, the shape and size of the elements, transportation, and
handling operations…etc. Moreover, a plethora of research and experimental work
has been conducted validating the different joints and connections design methods
used in FRP pultruded composites [45]–[50]
Pultruded structural shapes that imitate the geometry of structural steel sections
are assembled and constructed via bolting, as seen in Figure 66. However, the direct
application of connection technology from steel structures to FRP structures often
results in the oversizing of FRP components as it fails to consider the differences in
material behaviors, since FRP profiles have a linear-elastic behavior incompatible
with plastic deformations, leading to higher stress concentrations around bolt holes
than steel (which exhibits ductile behavior). Additionally, the anisotropic behavior
of FRP profiles imposes constraints as transverse stresses are inevitable. As a
result, the design is often limited by the load-bearing capacity of bolted connections, leading to uneconomical cross-section selection. FRP pultruded composites
can be connected using different methods, mainly: bolted, bonded, hybrid (bolted
and bonded), and interlock connections as discussed in the following sections.
8.3.1 Bolted Joint
Bolted connections are the most commonly type of joint used in FRP pultruded
structures. Bolted connections certain advantages when it comes to joints that
includes ease of installation, adjustability, as well as disassembly, if required. Additionally, bolted connections provide a method to connect FRP-to-steel members.
There are specific considerations when using bolted connections in FRP structures
the main ones are summarized below:
i.
Material Compatibility: The bolts, nuts, and washers used in FRP bolted
connections should be compatible with the FRP composite element and
constituents to prevent galvanic corrosion or other chemical reactions that
could compromise the integrity of the connection. Non-metallic or corrosion-resistant fasteners, such as fiberglass bolts can be used in FRP applications, but metallic based bolts, nuts, and washers are most used.
ii.
Hole Preparation: Proper hole preparation is crucial to avoid damage to the
FRP material, especially during the drilling process. The holes should be
drilled carefully with the appropriate size, avoiding excessive heat generation or delamination of the FRP laminate. Counterboring or countersinking
may be required to achieve flush or recessed bolt heads. Therefore, it is
preferable to have holes pre-drilled by the manufacturer rather than in the
field, although field drilling is also an option.
iii.
Joint Design: The joint design for bolted connections should consider the
specific requirements of the FRP structure such as the type and magnitude of loads and resulting stress and moments. Factors such as the thickness of FRP laminates, edge distance, and spacing between bolts should be
8. FRP DESIGN: GUIDELINES & JOINTS 97
iv.
v.
vi.
carefully determined to ensure
sufficient bearing strength and
prevent laminate failure. Reinforcement methods, such as
the use of doublers or locally
thickened regions, can be used
as part of the FRP pultruded
component fabrication to
enhance the strength and stiffness of the joint.
Torque and Tightening: Proper
torque control is essential
during the tightening of bolts
in FRP structures. Over-tightening can lead to damage or
Figure 66 – Left: Bolted connections between GFRP profiles of three-dimensional
crushing of the FRP laminate,
frame (Courtesy of Strongwell), and Right: pedestrian bridge assembly (Source:
while under-tightening can
fiberline composites).
result in insufficient clamping
force and reduced joint strength. During construction, torque values should
be followed, considering the specific properties of the FRP material and the
fasteners being used.
Gasket or Washer Selection: The selection of suitable gaskets or washers
is important in bolted connections to distribute the load evenly and minimize stress concentrations. Nonmetallic as well as metallic washers or
composite gaskets that are compatible with FRP materials are commonly
used to prevent damage to the laminate and ensure proper load transfer.
The gasket or washer selection is critical for the capacity of the pull-trough
limit state of connection design.
Inspection and Maintenance: Regular inspection and maintenance of
bolted connections is necessary to ensure their continued performance and
integrity. This may involve checking for signs of corrosion, monitoring
bolt tension, and performing any necessary adjustments or replacements to
maintain the desired clamping force.
8.3.2 Adhesive Joint
Adhesive bonding is a method for joining FRP components in various applications. It involves using specialized adhesives to create a strong and durable bond
between FRP materials. This connection method offers several advantages for FRP
structures, including load transfer efficiency, improved stress distribution, and the
ability to create complex shapes and connections. FRP-to-steel-adhesive joints
have also been used and extensively studied. There are several considerations to
account for when using adhesively bonded FRP connections:
i.
Adhesive Selection: The choice of adhesive is crucial for successful
bonding in FRP structures. The adhesive should be specifically designed
for bonding FRP materials and provide good compatibility with the
specific resin system and FRP element used. Adhesive manufacturers, as
well as FRP pultrusion manufacturers both typically provide technical data
and recommendations for selecting the appropriate adhesive for different
applications.
ii..
Surface Preparation: Proper surface preparation is essential for achieving
a reliable bond. The surfaces to be bonded should be clean, dry, and free
from contaminants such as dust, grease, or release agents. Surface preparation methods may include sanding, solvent cleaning, and using surface
conditioning techniques.
iii.
Adhesive Application: Adhesive applications should follow the manufacturer’s instructions, which typically involve using specific tools and
techniques to apply and spread the adhesive. It is important to apply the
98
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
adhesive uniformly and avoid excessive or insufficient application. Some
adhesives may require mixing or curing agents, and proper handling of
these components is necessary for achieving the desired bond strength.
iv.
Curing and Bond Strength Development: Adhesive bonding requires sufficient curing time to develop the desired adhesive bond strength. The curing
conditions, including temperature and humidity, should be controlled as
necessary, per the adhesive manufacturer’s recommendations. Adequate
curing ensures the development of the adhesive’s chemical and mechanical
properties for optimal bond performance.
v.
Joint Design and Surface Area: The joint design plays a significant role
in the bond strength and overall structural performance. Joints should be
designed to provide sufficient contact area between the bonded surfaces,
which improves load transfer and reduces stress concentrations. Proper
consideration of joint geometry, overlap length, and adhesive thickness is
important for achieving desired bond strength.
vi.
Testing and Quality Control: To ensure the reliability of adhesive bonding
in FRP structures, testing and quality control procedures are essential. This
may involve performing lap shear tests or other relevant mechanical tests on
bonded specimens to evaluate the bond strength, as previously discussed.
Quality control measures should be implemented throughout the manufacturing process to monitor and validate the adhesive bonding process.
While this connection method may not be as commonly used in building projects
due to site related constraints and the challenge of ensuring quality control, it is
often employed in combination with other connecting methods. Overall, adhesive
bonding is a well-suited method for the linear elastic and anisotropic nature of
FRP materials and provides smoother and more uniform load transfer compared
to bolting. Adhesive bonding also provides higher joint efficiency and stiffness,
which is important for stiffness-governed designs of structures made of FRP
pultruded components. Adhesive bonded joints are also lighter and do not require
drilled holes, reducing the risk of moisture ingress in the composite element during
service. Adhesively bonded connections have been mainly used in bridge decks to
join adjacent FRP panels and to join these panels to longitudinal girders, as seen in
Figure 67. They have also been used to assemble standard sections and create more
complex sections than those provided by manufacturers.
8.3.3 Hybrid Connections
Hybrid connections typically refer to the use of multiple types of connecting
methods or materials to join FRP pultruded elements. Typically, these connections
combine mechanical/interlocking (e.g. fastening with bolts) and adhesive bonding.
The objective of hybrid connections is to optimize the strength, stiffness, durability, and overall performance of the joint, but sometimes other driving design
factors may be prioritized. While adhesive jointing provides most of the stiffness,
bolts may be necessary to counteract deficient bonding execution, uncertainty,
or adhesive deterioration during service life. Additionally, bolts may be used to
fulfill strength requirements, while bonding is expected to help meet deformability
requirements. Moreover, clamping pressure applied in the bolts may improve
bonding performance hence a hybrid connection [35]. The considerations of both
bolted and adhesive joints need to be considered in hybrid joints as well.
It is worth pointing out that the hybrid connection that relies on both the bond
and mechanical fasteners to carry the load simultaneously is considered redundant
because the bolts are not carrying any load in an intact joint. Bolts are only mechanically engaged if the adhesive bond joint fails. Therefore, this type of connection
is not commonly used in FRP pultruded structures, as the adhesive bond is the
primary source of strength in combined connections. Instead, mechanical fasteners
are the preferred choice for FRP pultruded structural shapes and may use adhesion
as a redundant method. To design a mechanical connection for these structures, it
is essential to have a thorough understanding of their properties and characteristics,
including limit states and critical stresses [51].
8. FRP DESIGN: GUIDELINES & JOINTS 99
8.3.4 Interlocking Connections
Interlocking connections in FRP pultruded elements typically connect FRP
elements through a slot with a wedge-grooving mechanism, similar to joinery in
woodworking connections that do not involve adhesion or bolts (or screws in the
case of wood/timber). This specific type of connection with interlocking features
or profiles are design to securely join different FRP components without the need
for additional fasteners or adhesives that can provide strength, stability, and load
transfer between the pultruded components. This type of connection can also be
supplemented with mechanical fastening and/or adhesive bonding.
An established example for interlocking connection in FRP pultruded elements
is the Advanced Composite Construction System (ACCS) developed by Maunsells
Structural Plastic Ltd in which plank units (multi-cellular box sections) are assembled by sliding a toggle section into the groove of each panel, as seen in Figure
68. This type of connection is typically implemented in pedestrian bridge decks or
panels in a modular construction approach, which allows for quick construction
and erection times, but also requires high dimensional precision of the manufactured FRP pultruded components’ geometry and linearity.
8.3.5 Failure Modes: Bolted Joints
To gain a thorough understanding of how a bolted connection behaves in an
FRP structure, it is necessary to analyze its failure. While bolted joints in FRP
structures exhibit similar primary failure modes as those in metal structures, the
processes by which damage begins and spreads can vary significantly. As a result,
the conventional failure criteria used
for metals may not always be suitable in this context [52]. Typically,
stress concentration occurs around
bolted locations and joints in an FRP
structure, primarily due to abrupt
changes in stiffness. The presence of
holes created for structural members
contributes to further stress concentration by reducing the material’s
cross-section. The concentrated force
acting around these holes intensifies the stress concentration-related
responses. The strength of a joint is
influenced by the connections or holes
present in each direction of different
structural members coming together
at the joint. When mechanical connections are subjected to various loads
and moments in FRP structures, the
Figure 67 – FRP Bonded connections between GFRP panels of bridge decks
failure modes of mechanical fasteners
(Source: Creative Pultrusions)
usually fall into one of several categories as shown in Figure 69 [10].
i.
Bearing Failure: This type of
failure is local in the (bolt)
force transfer region. The
FRP structural members crush
locally, in the applied load
direction but do not cause
catastrophic failure ​[23]​.
Bearing failure is the localized compression failure in
the FRP plate near the bolt. It
is the most desirable and the
only failure that is less brittle.
Figure 68 – Interlocking connections in ACCS System (Source: Strongwell)
100
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Figure 69 – Classification of failure modes in bolted FRP joints [10]
Bearing is a damage-tolerant failure when the plate width-to-hole diameter ratio is high. It relies on lateral restraint that can delay delamination
cracking. The failure is progressive, indicated by the local buckling of
fibers and resin crushing. A less common name for bearing failure is longitudinal shear failure [53].
ii.
Tension Failure: when a specimen is narrow compared to the bolt diameter, the failure may be attributed to a crack propagating transverse to the
applied load direction [10]. The associated failure mechanism is assumed
to be caused by tangential or compression stresses at the hole edge and is
likely to occur when the hole-diameter-to-width ratio (d/w) is large, and the
bypass-to-bearing-load ratio is high. In this case, the cracks will propagate
in a transverse direction to the load direction[54].
iii.
Cleavage Failure: This type of failure mode, known as the shear-out
failure, can also sometimes be characterized by a single-plane “cleavage”
failure, where the apparent laminate transverse tensile strength is less than
the corresponding in-plane shear strength [10].
iv.
Shear-out Failure: This type of failure is predominant in the fiber direction
of unidirectional laminates. The section of structural members parallel to
the applied load direction pushes past the remaining structural members,
meeting at a joint. Shear-out failures should be regarded as a special case of
bearing failures. In most cases, the shear-out failure is a consequence of a
bearing failure with a short edge distance. However, for highly orthotropic
composites, shear-out failures occur at very large edge distances. Shear-out
failure is a combination of in-plane and interlaminar shear failures. The
shear-out failure can also be characterized by a single-plane “cleavage”
failure, where the apparent laminate transverse tensile strength is less than
the corresponding in-plane shear strength. Bolted composite joints are
usually designed to avoid this brittle mode of failure [54].
v.
Block Shear Failure: When a connection is subjected to both shear and
tensile loads, it could experience a block shear failure. A good example of
this is a beam that is coped at the location of the connection. This type of
failure combines a net-tension and shear-out failure, they cannot be treated
separately. An interaction equation between the two limit states is used in
the design [51].
By understanding the fundamental factors that influence bolted joint failure and
corresponding strength, it is possible to realize the relative simplicity of such joints.
Despite the anisotropic nature and lack of ductility of FRP pultruded composites,
bolted composite joints fail in a fashion like metallic joints. However, because no
yielding occurs in composites, the failure mechanisms of composites and metallics
are completely different from each other (ASTM 2002). In fact, the design of FRP
bolded connections may be considered more simplistic due to certain constraints
8. FRP DESIGN: GUIDELINES & JOINTS 101
relevant to the properties of FRP composites, which facilities the design for this
type of joints. Several factors influence the modes of failure of pultruded composites[54], with the primary factors summarized as follows:
i.
Geometrical Factors: these factors are based on the pultruded element
width, edge distance, overall thickness, hole diameter… etc., as referenced
in Figure 70.
ii.
Materials Factors: these factors are based on the resin matrix and fiber
type, fillers content and volume fraction, fiber surface treatment…etc.
iii.
Fasteners Factors: these factors relate to the type of fastener, the fastener
size, hole size and tolerance, as well as the applied torque on the fastener.
iv.
Design Factors: these factors range from the joint type, loading directions,
loading rate, as well as type of loading: static versus dynamic loading…etc.
Figure 70 – Minimum requirements spacing for bolted connection geometries. (ASCE 2010)
102
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
v.
Long-term and Environmental Exposure Factors: these factors range from
creep limit and creep rupture, exposure to humidity, temperature cycling,
chemical attacks, stress corrosion…etc.
In comparison with steel bolted joints, slip-critical connections are not permitted
in FRP pultruded elements. This is well established because pultruded connections
cannot be relied on to develop any frictional capacity (or slip-critical capacity),
due to the properties of the base pultruded material. Higher bolt torques may create
a misleading impression of the strength of the connection, which realistically can
only be designed as a ‘bearing’ connection.
Conventional FRP pultruded materials have low through-the-thickness stiffness and strength properties, making them susceptible to crushing under high
bolt torques. Since the base material can creep, the bolt tension can decrease over
time, due to strain relaxation. If FRP bolts are used, the bolts themselves will
lose tension due to strain relaxation. In addition, if small nuts (without washers)
are used, the entire fastener can punch through or crush the base pultruded material when the connection is loaded. For this reason, only bearing connections are
possible in pultruded bolted connections; slip-critical or friction connections are
not feasible in pultruded connections [7].
8.3.6 FRP vs Metallic Bolted Connections
Understanding the key underlying differences between FRP and metallic bolted
type of connections will help engineers and designers that are familiar with
the design of metallic based bolted connections, implement FRP based bolted
connections.
Bolted FRP pultruded connections can fail differently from steel connections,
despite similar connection geometries, due to the mismatch in strength and stiffness between FRP and steel, among other factors. Therefore, understanding the
key differences in failure modes between FRP and metallic bolted connections can
enhance the implementation of FRP bolted connections, summarized as follows:
i.
Load Distribution: In an FRP connection, the load is distributed differently
between the different rows of fasteners, similar to wood connections but
different from steel connections where it is assumed that the load is transferred evenly among all of the bolts [51].
ii.
Notch Sensitivity: The higher notch sensitivity of FRP structural members
when compared to conventional steel structural members is a key factor,
resulting in higher stress concentration around the perimeter of a hole in
bolted connections.
iii.
Brittleness: The higher brittleness (relative lack of ductility) of FRP structural members results in higher stress concentration around the perimeter
of a hole when compared to steel bolted connections.
iv.
Materials: The influence of the constituent materials of the FRP pultruded
parameters such as fiber volume fraction, resin properties, voids, or
stacking sequence is very different to the isotropic nature of steel members,
hence affecting the response of the connection.
v.
Connection Parts: In pultruded connections the failure can be due to
the pultruded material of the members being connected, in the pultruded
material of the pultruded connection parts (angles and gussets), or in the
mechanical fasteners themselves (the bolts, nuts, rods, and washers).
8.3.7 Failure Modes: Adhesive Joints
Adhesive failure refers to the failure or separation of the adhesive bond between
FRP materials or between FRP pultruded elements and other substrates (concrete,
steel, timber…etc.). Looking at adhesive failure between FRP pultruded elements,
this can occur due to various factors, and understanding the different failure modes
is important for designing reliable adhesive joints. Here are some common adhesive failure modes in FRP structures as presented in Figure 71 [10]:
i.
Cohesive Failure: Cohesive failure occurs within the adhesive itself. It
happens when the adhesive material breaks or separates along its internal
8. FRP DESIGN: GUIDELINES & JOINTS 103
Figure 71 – Adhesive failure mode schematic
layers (or bulk of the adhesive). Cohesive failure typically indicates that
the adhesive itself is not able to withstand the applied load, and it may be
attributed to factors such as inadequate adhesive strength or insufficient
bond thickness.
ii.
Interfacial Failure: Interfacial failure occurs at the interface between the
adhesive and the adherend being the FRP material (or other substrate). This
failure mode suggests that the bond strength at the interface is weaker than
the cohesive strength of the adhesive. Interfacial failure can be caused by
factors such as inadequate surface preparation, poor adhesive wetting or
penetration, or contaminants on the adherend surface.
iii.
Adhesive Shear Failure: Adhesive shear failure occurs when the adhesive
bond fails due to either tensile-shear (in-plane) and/or torsion-shear (outof-plane) forces acting parallel to the bonded interface, and thus the bonded
connector resistance is limited by the shear strength of the adhesive. Adhesive shear failure is commonly observed in applications where the bond is
subjected to high shear and/or peel stresses.
iv.
Adhesive Peel Failure: Adhesive peel (or cleavage) failure occurs when the
adhesive bond fails due to peeling or pulling forces acting perpendicular to
the bonded interface. This failure mode is common in applications where
the bond is subjected to bending, flexing, or tensile loads that cause the
adhesive to peel away from the adherend. It is the weakest failure mode
related to adhesive joints. It should be noted that cleavage failure is often
found on thick sections, while the peel failure is found when thin sections
are connected.
v.
Degradation: Adhesive failure in FRP structures can also be influenced
by environmental factors. Exposure to moisture, temperature variations,
UV radiation, or chemical agents can degrade the adhesive’s properties,
leading to reduced bond strength and eventual failure.
Ultimately, the general design purpose of an adhesive joint is to cause failure
on the FRP structural components/s that are being connected by rupture or other
failure. This is achieved by ensuring that the bonded connection with adhesive is
strong and adequately transfers the loads to the FRP components, not failing in
the adhesive. Thus, the FRP structural members if under tension loads (outside the
joint locations) will rupture due to stress concentration effects at corners, with a
sudden change in stiffness at/or near the corner locations.
There are several limitations on adhesively bonded joints that are important
to recognize. In practice, the adhesively bonded connections have been limited
because of the absence of certain issues including [55]:
i.
Long-Term Behavior: There is insufficient data, assuming a standard
50-year service life for built infrastructure, to fully understand the longterm behavior of adhesives under varying environmental conditions from a
reliability standpoint.
ii.
Analysis: Accurate analysis methods to evaluate stress and strain distributions around joints and along the length of an adherend under varying load
conditions is a complex process, and analysis assumptions applied to the
104
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
design can vary greatly the resulting theoretical joint strength. Additional
work is needed to reliably analyze completed adhesive joints.
iii.
Materials: Reliable materials properties of adhesives, including the reliability when being applied in the field, under the variability of installation,
and practical installation difficulties presents too many uncertainties that
need to be better understood and evaluated.
In addition, failure modes of bonded connections are influenced significantly by
defects and voids, thickness variations, environmental effects, and processing variations of adhesives. It is equally important to note that failure of bounded connections may depend on deficiencies in surface preparation [10].
Due to the aforementioned limitations, adhesively bonded-only connections are
rarely used in pultruded structures. Moreover, when used in hybrid connections,
the contribution of the adhesive-bond joint is typically not included in full within
the design. The long-term properties of pultruded connections under sustained
loads using currently available adhesives in corrosive environments, typical for
pultruded structures, are still the subject of active research [5], [56].
The use of adhesive bonding in addition to bolting in pultruded connections is
typically recommended directly by pultrusion manufacturers. Although bonding
does not generally increase the ultimate capacity of the connection, it does improve
the connection stiffness, especially when oversized holes and nontensioned bolts
are used, as is generally the case in conventional pultruded construction. This
improves the serviceability of the connection with respect to rotations under
service loads and with respect to durability of the connection. However, it has been
shown in numerous studies that this increased initial stiffness comes at the expense
of the connection ductility, and bonded-and-bolted connections tend to fail in a
brittle fashion, whereas bolted-only connections tend to fail in a much more ductile
fashion. The ultimate moment capacity of the connection is, however, not typically increased using the adhesive. The adhesive typically fails in tension or shear
at a low strain, and when this happens, all the load is suddenly transferred to the
mechanical fasteners, which leads to brittle failure of the connection [7].
9. CONCLUDING REMARKS AND FUTURE WORK105
9. CONCLUDING REMARKS AND FUTURE WORK
Non-metallic (NM) pultruded composites, known as Fiber fiber-reinforced
polymer (FRP) composites, provide durable and cost-effective solutions that have
been extensively tested and validated as an alternative to traditional building
materials (such as wood, steel, aluminum). FRP composites are an enabling material solution for the building industry that can increase productivity and speed of
construction; as demonstrated by numerous construction projects. The economic
and performance advantages of FRP pultruded composites compared to traditional
building materials are evident.
Today, FRPs are supported by accepted and recognized material, design, and
standards; however. While the lack of familiarity and awareness by engineers,
owners, and specifiers is a persistent barrier for widespread adoption; the growing
acceptance and maturity of manufactured pultruded composites can be widespread
to multiple built infrastructure applications.
This document has provided a comprehensive and up-to-date overview of properties, design, and use of FRP pultruded components, their connection methods
and resulting structures, with the underlying objective to aid stakeholders in the
implementation within building applications and beyond.
9.1 CONCLUSIONS
• FRP Pultruded Elements: The FRP structural shapes are predominantly manufactured using a primarily glass fibers with a variety of other available fibers
such as basalt, carbon, and aramid. These fibers are combined with resins
like epoxy, vinyl ester, polyester, and polyurethane to create composites with
distinct mechanical properties, thereby offering a wide range of applicationspecific solutions.
• Key Benefits: The advantages of FRP pultruded materials are multi-faceted.
FRPs offer corrosion resistance, making them ideal for use in harsh environments, resulting in long life-cycle service, and reducing maintenance costs. It
is lightweight (approximately 1/4 that of steel), reducing transportation costs,
facilitating the ease of handling and installation, thereby reducing construction
and labor costs. Additionally, the high tensile strength and non-interference
with magnetic fields and radar frequencies make them versatile for various
applications.
• Applications: FRP materials have permeated multiple industries, from aerospace to the military. In the construction sector, its use is extensive from
structural framing, concrete reinforcement, panels, gratings, and waterfront
structures like fender systems and marinas. Their versatility is also evident
in transportation infrastructure, where they are used in platforms, posts, and
fences.
• Testing Standards: FRP materials undergo rigorous testing at three levels:
constituent (fiber/resin), composite (lamina/laminate), and full-section tests.
Standards developed by ASTM and ISO are commonly followed. The growing
interest in non-destructive testing methods is particularly noteworthy for
quality control and structural health monitoring.
• Specifications: Material, design, and component specifications exist but are
fragmented. Gaps are evident in the long-term durability performance and fire
performance criteria of these materials, as they vary across applications. A
unified approach to testing and specification is needed, along with applicationspecific standards.
• Design Standard: The recent approval of ASCE/SEI-74 ‘LRFD for Pultruded
FRP Structures’ is a landmark achievement, announced at the 2023 North
American Pultrusion Conference. This standard has undergone extensive
review and is expected to be published, setting a design benchmark for the
FRP pultruded industry.
106
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
9.2 FUTURE WORK
Areas that will support the continued adoption of FRP pultruded elements in the
built environment include:
• Design Manual: Developing a supporting companion to the ASCE/SEI-74
design standard following the equivalent form and structure of the Steel
Designer’s Manual, that provides a detailed description of the design process
for a pre-selected range of structural elements and applications, will accelerate
the learning curve by all users.
• Design Examples: Step-by-step design examples similar to AISC steel design
guide series, that provides practical commentary on the process and rationale
for FRP pultruded design on axial compression (including global and local
buckling) flexural, shear, and bolted connection will enable design engineers
to efficiently and quickly design FRP structures, saving time and effort.
• Knowledge Transfer and Education: Educational resources that support both
tenured and young engineers are needed to disburse and transfer knowledge
of FRP pultruded solutions. Training, workshops, and other design tools that
encapsulate the collective knowledge and experience of the industry will be
needed, allowing for knowledge transfer between all stakeholders.
• Production and Installation: Recognition of fabrication and installation of
pultruded FRP structures standard requirements such as [38] across stakeholders for the general and specific applications that consider the quality
management aspects, design quality, and execution quality of the FRP
pultruded elements is needed.
• Maintenance and Repair: Maintenance and repair guidelines based on the
different FRP pultruded composite applications is needed, especially as FRP
solutions gain prominence. Such guides need to leverage readily available
non-destructive testing and evaluation methods as tools to support infrastructure owners in the maintenance and repair activities to assure the extended
service life os such composites structures.
• Specifications gap: Long-term durability and fire performance criteria and
specifications based on different FRP pultruded applications needs to be
developed and referenced, ensuring homogeneity between industry bodies,
academic institutions, and regulatory agencies. A concerted effort is required
to unify the fragmented standards and specifications.
10. REFERENCES107
10. REFERENCES
[1]
F. C. McCormick, “Advancing structural plastics into the future,” Journal
of Professional Issues in Engineering Education and Practice, vol. 114, no. 3, pp.
335–343, 1988, doi: 10.1061/(ASCE)1052-3928(1988)114:3(335).
[2]
ASCE, “Structural Plastics Design Manual, ASCE Manuals and Reports
on Engineering Practice 63, American Society of Civil Engineers, Reston, VA.,”
1984.
[3]
H. Smallowitz, “Reshaping the Future of Plastic Buildings,” Civil Engineering—ASCE, vol. 55, no. 5, pp. 38–41, 1985.
[4]
A. Green, T. Bisarnsin, and E. A. Love, “Pultruded reinforced plastics
for civil engineering structural applications,” Journal of reinforced plastics and
composites, vol. 13, no. 10, pp. 942–951, 1994.
[5]
T. Keller, “Towards structural forms for composite fibre materials,” Structural engineering international, vol. 9, no. 4, pp. 297–300, 1999.
[6]
C. E. Bakis et al., “Fiber-reinforced polymer composites for construction—State-of-the-art review,” Journal of composites for construction, vol. 6, no.
2, pp. 73–87, 2002.
[7]
L. Bank, Composites for construction: structural design with FRP materials. 2006.
[8]
G. ’ Boscato, C. Casalegno, and S. Russo, “DESIGN OF FRP STRUCTURES IN SEISMIC ZONE,” 2018. [Online]. Available: http://www.cnr.it/sitocnr/
IlCNR/Attivita/NormazioneeCertificazione/DT205_2007.html.
[9]
R. Meyer, Handbook of pultrusion technology. Springer Science & Business Media, 2012.
[10] H. V. S. GangaRao and W. Prachasaree, FRP composite structures: theory,
fundamentals, and design. CRC Press, 2021.
[11] G. Lubin, “Handbook of Composites; Lubin, G., Ed.” Springer: Boston,
MA, USA, 1982.
[12] P. Mallick, “Fiber Reinforced Composites Materials, Manufacturing, and
Design,” 1993.
[13] J. T. Mottram and J. Henderson, “Fibre-Reinforced Polymer Bridges—
Guidance for Designers,” CIRIA: London, UK, 2018.
[14] Y. Yang, X. Wang, and Z. Wu, “Life cycle cost analysis of FRP cables for
long-span cable supported bridges,” 2020, doi: 10.1016/j.istruc.2020.02.019.
[15] T. Cadenazzi, G. Dotelli, M. Rossini, S. Nolan, and A. Nanni, “Cost and
environmental analyses of reinforcement alternatives for a concrete bridge,” Taylor
& Francis, 2020, Accessed: Jun. 15, 2023. [Online]. Available: https://www.tandfonline.com/doi/abs/10.1080/15732479.2019.1662066
[16] Strongwell C, “FRP Specifications Section 06 71 00 Fiberglass Reinforced Polymer (FRP) Structural Shapes/Plate and Fabrications.” [Online]. Available: www.strongwell.com
[17] C. Pultrusions, “The Pultex ® Pultrusion Design Manual STANDARD
AND CUSTOM FIBER REINFORCED POLYMER STRUCTURAL PROFILES
FEATURING • Pultex ® Standard Structural Profiles • Pultex ® SuperStructural
Profiles Nuclear test tower constructed using Pultex ® Standard Structural Profiles
The New and Improved Pultex ® Pultrusion Global Design Manual Contents,”
2023.
[18] A. Vedernikov, A. Safonov, F. Tucci, P. Carlone, and I. Akhatov, “Pultruded
materials and structures: A review,” J Compos Mater, vol. 54, no. 26, pp. 4081–
4117, 2020.
[19] H.-Y. Kim and S.-Y. Lee, “Static and fatigue load performance of a
pultruded GFRP deck panel reinforced with steel wires,” Compos Struct, vol. 207,
pp. 166–175, 2019.
[20] D. Zhang, Y. Lv, Q. Zhao, and F. Li, “Development of lightweight emergency bridge using GFRP–metal composite plate-truss girder,” Eng Struct, vol.
196, p. 109291, 2019.
108
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
[21] F. Ascione, G. Mancusi, S. Spadea, M. Lamberti, F. Lebon, and A. MaurelPantel, “On the flexural behaviour of GFRP beams obtained by bonding simple
panels: an experimental investigation,” Compos Struct, vol. 131, pp. 55–65, 2015.
[22] A. Quadrino, R. Penna, L. Feo, and N. Nisticò, “Mechanical characterization of pultruded elements: Fiber orientation influence vs web-flange junction local
problem. Experimental and numerical tests,” Compos B Eng, vol. 142, pp. 68–84,
2018.
[23] M. Zoghi, The international handbook of FRP composites in civil engineering. Crc Press, 2013.
[24] S. Kanagaraj and S. Pattanayak, “Measurement of the thermal expansion
of metal and FRPs,” Cryogenics (Guildf), vol. 43, no. 7, pp. 399–424, 2003.
[25] L. A. Carlsson, D. F. Adams, and R. B. Pipes, Experimental characterization of advanced composite materials. CRC press, 2014.
[26] V. M. Karbhari et al., “Durability gap analysis for fiber-reinforced polymer
composites in civil infrastructure,” Journal of composites for construction, vol. 7,
no. 3, pp. 238–247, 2003.
[27] K. Liao, C. R. Schultesiz, D. L. Hunston, and L. C. Brinson, “Long-term
durability of fiber-reinforced polymer-matrix composite materials for infrastructure applications: a review,” 1998.
[28] M. A. G. Silva and H. Biscaia, “Degradation of bond between FRP and
RC beams,” Compos Struct, vol. 85, no. 2, pp. 164–174, 2008.
[29] E. N, “Reinforced plastics composites—Specifications for pultruded
profiles. Part 2: Methods of test and general requirements,” 2003.
[30] I. Nishizaki and S. Meiarashi, “Long-term deterioration of GFRP in water
and moist environment,” Journal of composites for construction, vol. 6, no. 1, pp.
21–27, 2002.
[31] D. K. Hsu, D. J. Barnard, J. J. Peters, and V. Dayal, “Physical basis of
tap test as a quantitative imaging tool for composite structures on aircraft,” in AIP
Conference Proceedings, American Institute of Physics, 2000, pp. 1857–1864.
[32] Tom Nelligan and Daniel Kass, “Ultrasonic testing provides a ready and
well-established technique for locating and documenting internal flaws.,” Aug. 11,
2014. https://www.qualitymag.com/articles/92050-ultrasonic-testing-of-fiberglassand-carbon-fiber-composites (accessed Jun. 01, 2023).
[33] B. Wang, S. Zhong, T.-L. Lee, K. S. Fancey, and J. Mi, “Non-destructive
testing and evaluation of composite materials/structures: A state-of-the-art review,”
Advances in mechanical engineering, vol. 12, no. 4, p. 1687814020913761, 2020.
[34] S. Gholizadeh, “A review of non-destructive testing methods of composite
materials,” Procedia structural integrity, vol. 1, pp. 50–57, 2016.
[35] J. Bai, Advanced fibre-reinforced polymer (FRP) composites for structural applications. Woodhead Publishing, 2022.
[36] E. 13706 CEN, “Reinforced Plastics Composites—Specifications for
Pultruded Profiles. Part 1: Designation; Part 2: Methods of Test and General
Requirements; Part 3: Specific Requirements,” 2002.
[37] A. N. 15708–1 ABNT, “Petroleum and Natural Gas Industries – Pultruded
Shape Part 1: Materials, Test Methods and Dimensional Tolerances, Brasilian
Association of Technical Standards,” Rio de Janeiro, 2011.
[38] ACMA, “American Composites Manufacturers Association (ACMA)
Code of Standard Practice for Fabrication and Installation of Pultruded FRP Structures, 2nd ed.”
[39] D. Pirchio, “Advancements in the Design of Pultruded Fiber Reinforced
Polymer (FRP) Structures,” 2023, doi: 10.7274/NC580K25P40.
[40] American Society of Civil Engineers. (2024). Load and Resistance Factor
Design (LRFD) for Pultruded Fiber Reinforced Polymer (FRP) Structures. https://
doi.org/10.1061/9780784415771
[41] ASCE/ACMA, “Load and Resistance Factor Design (LRFD) for Pultruded
Fiber Reinforced Polymer (FRP) Structures,” 2022, doi: 10.1061/9780784415771.
10. REFERENCES109
[42] CEN/TS, “Design of fiber-polymer composite structures (CENTS1910-EEN),” 2022.
[43] American Wood Council, NDS National Design Specification for Wood
Construction: With Commentary. American Wood Council, 2018.
[44] ASCE/SEI 7–10, “Minimum Design Loads for Buildings and Other
Structures,” Alexander Bell Drive, 2010.
[45] K. Perumal and N. Pannirselvam, “Approaches for the Statistical Assessment on Structural Joints of Pultruded Fiber-Reinforced Polymer Profiles Using
Trend Analysis,” Iranian Journal of Science and Technology, Transactions of
Civil Engineering, vol. 47, no. 1, pp. 21–45, 2023.
[46] J. Qureshi, Y. Nadir, S. J.-C. Structures, and undefined 2020, “Bolted and
bonded FRP beam-column joints with semi-rigid end conditions,” Elsevier, 2020.
[47] F. Feroldi and S. Russo, “Structural behavior of all-FRP beam-column
plate-bolted joints,” Journal of Composites for Construction, vol. 20, no. 4, p.
04016004, 2016.
[48] A. M. G. Coelho and J. T. Mottram, “A review of the behaviour and
analysis of bolted connections and joints in pultruded fibre reinforced polymers,”
Mater Des, vol. 74, pp. 86–107, 2015.
[49] T. Vallée, T. Tannert, R. Meena, S. H.-C. P. B. Engineering, and undefined 2013, “Dimensioning method for bolted, adhesively bonded, and hybrid
joints involving Fibre-Reinforced-Polymers,” Elsevier, 2013.
[50] D. Duthinh, “Connections of fiber-reinforced polymer (FRP) structural
members: a review of the state of the art,” 2000.
[51] R. Sommer, “Fiber reinforced polymer (FRP) pultruded shape structural
connections,” 2011.
[52] K. D. Weimert, Bolted Connection Strength in Pultruded Glass Fiber
Reinforced Polymer Structural Shapes. West Virginia University, 2015.
[53] J. Qureshi, “A Review of Fibre Reinforced Polymer Structures,” Fibers,
vol. 10, no. 3. MDPI, Mar. 01, 2022. doi: 10.3390/fib10030027.
[54] A. Mosallam, “Design guide for FRP composite connections,” American
Society of Civil Engineers, 2011.
[55] L. F. M. da Silva, A. Öchsner, and R. D. Adams, Handbook of adhesion
technology, vol. 1. Springer, 2011.
[56] J. Cadei and T. Stratford, “8.1 The design, construction and in-service
performance of the all-composite Aberfeldy footbridge,” in Advanced Polymer
Composites for Structural Applications in Construction: Proceedings of the First
International Conference, Held at Southampton University, UK, on 15-17 April
2002, Thomas Telford Publishing, 2002, p. 445.
110
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
11. FRP COMPOSITE MANUFACTURERS
Company name
Creative Composites Group; dba Creative Pultrusions, Inc.
214 Industrial Lane, Alum Bank, PA 15521
Company Address
Company Website
www.creativecompositesgroup.com
Contact Person
Dustin Troutman
Company Phone
(814) 839-4186
Phone
(814) 285-6824
Company Email
ccg@pultrude.com
info@creativecompositesgroup.com
Email
dtroutman@pultrude.com
Company name
STRONGWELL®
Company Address
400 Commonwealth Ave, Bristol, VA 24201
Company Website
www.strongwell.com
Contact Person
Bhyrav Mutnuri
Company Phone
276 645 8000
Phone
276 645 8078
Company Email
info@strongwell.com
Email
bmutnuri@strongwell.com
ANNEX A: TERMINOLOGY USED WITH NM FRP PULTRUDED COMPONENTS111
ANNEX A: TERMINOLOGY USED WITH NM FRP PULTRUDED
COMPONENTS
A
ABSORPTION - A process in which one material takes in or absorbs another.
ADDITIVE - An ingredient blended into a resin to enhance or impart additional
physical properties. Common filler additives include fire retardants, pigments, and
ultraviolet inhibitors, among many others.
ADHESION - The state in which two surfaces are held together at an interface
by forces or interlocking action or both.
ADHESIVE - A substance capable of holding two materials together by surface
attachment. In the handbook, the term is used specifically to designate structural
adhesives, those which produce attachments capable of transmitting significant
structural loads.
AGING - The effect on materials of exposure to an environment for a period of
time; the process of exposing materials to an environment for an interval of time.
ANISOTROPIC - Not isotropic; having mechanical and/or physical properties which vary with direction relative to natural reference axes inherent in the
material.
ARAMID - A type of highly oriented organic material derived from polyamide
(nylon) but incorporating aromatic ring structure.
AREAL WEIGHT OF FIBER -- The weight of fiber per unit area of prepreg.
This is often expressed as grams per square meter.
ASPECT RATIO -- In an essentially two-dimensional rectangular structure
(e.g., a panel), the ratio of the long dimension to the short dimension. However, in
compression loading, it is sometimes considered to be the ratio of the load direction dimension to the transverse dimension. Also, in fiber micro-mechanics, it is
referred to as the ratio of length to diameter.
B
BATCH (OR LOT) - In general, a quantity of material formed during the same
process and having identical characteristics throughout. A batch of prepreg is
defined as a quantity which is produced from a single batch of matrix material
and fiber. The prepreg batch is produced at one time in the same equipment under
identical conditions.
BEARING AREA - The product of the pin diameter and the specimen thickness.
BEARING LOAD - A compressive load on an interface.
BEARING YIELD STRENGTH - The bearing stress at which a material
exhibits a specified limiting deviation from a linear stress-strain relationship.
BLEEDER CLOTH - Material, such as fiberglass, used in the manufacture of
composite parts to allow the escape of excess gas and resin during cure. The bleeder
cloth is removed after the curing process and is not part of the final composite.
BOND - The adhesion of one surface to another, with or without the use of an
adhesive as a bonding agent.
BRAIDING - Weaving of fibers into 3-dimensional shapes instead of flat tape
or fabric.
BREATHER CLOTH - A layer or layers of open weave cloth used to enable
the vacuum to reach the area over the laminate being cured, such that volatiles and
air can be uniformly removed. The uniform application of vacuum is required to
evenly apply pressure over the surface of the laminate.
BUCKLING (COMPOSITE) - A mode of structural response characterized
by an out-of-plane material deflection due to compressive or shear load on the
structural element involved. Buckling may take the form not only of conventional
general instability and local instability but also a micro-instability of individual
fibers.
112
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
C
C-SCAN - The record of the through transmission ultrasonic inspection, a
nondestructive inspection (NDI) technique for finding voids, delaminations,
defects in fiber distribution, etc.
CARBON FIBERS - Fibers produced by the pyrolysis of organic precursor
fibers such as rayon, polyacrylonitrile (PAN), or pitch in an inert atmosphere. The
term is often used interchangeably with “graphite”; however, carbon fibers and
graphite fibers differ in the temperature at which the fibers are made and heattreated, and the amount of carbon produced. Carbon fibers typically are carbonized
at about 2400°F (1300-C°) and assay at 93 to 95% carbon, while graphite fibers
are graphitized at 3450°F to 5450°F (1900 to 3000°C) and assay at more than 99%
elemental carbon.
CATALYST - A chemical which promotes a chemical reaction without becoming
a part of the molecular structure of the product. In resin systems, catalysts and
accelerators lower the temperature at which significant amounts of reaction occur,
affecting reaction rate and changing the characteristics of the cure cycle.
CAUL PLATES - Smooth plates, free of surface defects, used during the curing
process to transmit normal pressure and/or to provide a controlled surface on the
finished laminate.
CERAMIC TOOLING - Use of a castable ceramic to make a tool shape.
Ceramic tooling is seldom used unless a very large number of complex parts are to
be made; otherwise, tooling such as graphite tooling is more cost effective.
CLOTH - A woven product made from continuous yarns or tows of fiber.
“Cloth” and “fabric” are usually used interchangeably.
COCURING - The act of curing a composite laminate and simultaneously
bonding it to some other prepared surface during the same cure cycle.
COEFFICIENT OF LINEAR THERMAL EXPANSION - The change in
length per unit length resulting from a one-degree rise in temperature.
COMPOSITE - A matrix material reinforced with continuous filaments. The
constituents retain their identities in the composite; they do not dissolve or merge
completely into each other although they act in concert.
COMPOSITE SHEET - A sheet material comprised of a fiber reinforced
composite core sandwiched on either side by sheet metal. Typical sheet metals
used in composite panels include aluminum, steel, and stainless steel.
COMPOUND - An intimate mixture of polymer or polymers with all the materials necessary for the finished product.
COMPRESSION MOLDING - Putting a reinforced resin into a mold cavity,
closing the mold, and applying pressure and heat in order to force the material to
completely fill the mold cavity and to cure the material.
CONSOLIDATION - In metal matrix or thermoplastic composites, the diffusion bonding operation in which an oriented stack of plies is transformed under
heat and pressure into a finished composite laminate.
CONSTITUENT - In general, an element of a larger grouping. In advanced
composites, the principal constituents are the fibers and the matrix.
CONTINUOUS FILAMENT - A yarn or strand in which the individual filaments are substantially the same length as the strand.
CORROSION BARRIER - A laminate applied to a substrate to enhance its
corrosion resistance properties. In FRP products, corrosion barriers typically
consist of a resin-rich layer that improves resistance to corrosion, and often chemicals and abrasion, as well.
COUPLING AGENT - Any chemical substance designed to react with both
the reinforcement and matrix phases of a composite material to form or promote
a stronger bond at the interface. Coupling agents are applied to the reinforcement
phase from an aqueous or organic solution or from a gas phase, or added to the
matrix as an integral blend.
CROSSLINKING - Chemical reaction between molecules resulting in the
formation of a three-dimensional network of molecules. Crosslinking requires that
at least one of the molecules involved in the reaction have three or more reactive
ANNEX A: TERMINOLOGY USED WITH NM FRP PULTRUDED COMPONENTS113
groups; otherwise, the reaction only results in forming a longer molecule (chain
extension).
CRYSTALLINITY - Polymers, such as nylon, form localized areas of crystallinity (highly ordered sections) formed by alignment of sections of a polymer
chain (by folding, etc.) or of adjacent molecules. The localized areas of crystallinity change the physical behavior of the polymer.
CURE - To change the properties of a thermosetting resin irreversibly by chemical reaction. Cure may be accomplished by addition of curing agents, with or
without catalyst, and with or without heat and pressure.
CURE CYCLE - The time/temperature/pressure cycle used to cure a thermosetting resin system or prepreg.
CURE STRESS - A residual internal stress produced during the curing cycle of
composite structures. Normally, these stresses originate when different components
of a lay-up have different thermal coefficients of expansion. DAM - Boundary
support used to prevent excessive edge bleeding of a laminate and to prevent
crowning of the bag.
D
DEBOND - A deliberate separation of a bonded joint or interface, usually for
repair or rework purposes. (see Disbond, Unbond).
DEFORMATION - The change in shape of a specimen caused by the application of a load or force.
DEGRADATION - A deleterious change in chemical structure, physical properties or appearance.
DELAMINATION - The separation of the layers of material in a laminate. This
may be local or may cover a large area of the laminate. It may occur at any time
in the cure or subsequent life of the laminate and may arise from a wide variety of
causes.
DENIER - A textile term for the weight, in grams, of 9000 meters of fiber tow.
DENSITY - The mass per unit volume.
DESORPTION - A process in which an absorbed or adsorbed material is
released from another material. Desorption is the reverse of absorption, adsorption, or both.
DIELECTRIC CONSTANT - The ratio of the capacity of a condenser having
a dielectric constant between the plates to that of the same condenser when the
dielectric is replaced by vacuum; a measure of the electrical charge stored per unit
volume at unit potential.
DIELECTRIC STRENGTH - The average potential per unit thickness at
which failure of the dielectric material occurs.
DIELECTROMETRY - Use of electrical techniques to measure the changes in
loss factor (dissipation) and in capacitance during cure of the resin in a laminate.
DOUBLE TEE BEAM - A load-bearing structural component that resembles
two T-beams, side by side. A double tee beam consists of two vertical legs and a
horizontal flange along the deck. The flange and legs are integrally molded for to
create an exceptionally reliable structure capable of supporting heavy loads.
DRAPE - The ability of a prepreg to conform to a contoured surface. If the resin
becomes hard because of loss of solvent or staging, the prepreg becomes stiff and
loses its drape characteristics.
DRY FIBER AREA - Area of fiber not totally encapsulated by resin.
DUCTILITY - The ability of a material to deform plastically before fracturing.
E
EDGE BLEED - Removal of volatiles and excess resin through the edge of
the laminate, as in matched die molding of a laminate. In autoclaved parts, edge
bleeding is not recommended since excess resin will only be removed from the
area near an edge, resulting in uneven resin distribution.
ELASTICITY - The property of a material which allows it to recover its original size and shape immediately after removal of the force causing deformation.
114
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
ELASTOMERIC TOOLING - A tooling system utilizing the thermal expansion of rubber materials to form composite hardware during cure.
ELONGATION - The increase in gage length or extension of a specimen during
a tension test, usually expressed as a percentage of the original gage length.
END - A single fiber, strand, roving or yarn incorporated into a product. An end
may be an individual wrap yarn or cord in a woven fabric. In referring to aramid
and glass fibers, an end is usually an untwisted bundle of continuous filaments.
EPOXY RESIN - Resins which may be of widely different structures but are
characterized by the presence of the epoxy group. (The epoxy or epoxide group is
usually present as a glycidyl ether, glycidyl amine, or as part of an aliphatic ring
system. The aromatic epoxy resins are normally used in composites.)
EXTENSOMETER - A device for measuring linear strain.
F
FABRIC - A material constructed of interlaced yarns, fibers or filaments. Used
interchangeably with “cloth”.
FABRICATION - (1) Secondary processes performed on FRP sheets/panels.
These additional operations may include cutting to size, drilling holes, assembly,
and more. (2) The process of mixing plastic resin with thin glass fibers and additives to create fiber reinforced polymer.
FIBER - A single homogeneous strand of material, essentially one-dimensional
in the macrobehavioral sense, used as a principal constituent in composites because
of its high axial strength and modulus.
FIBER CONTENT - The amount of fiber present in a composite. This is usually
expressed as a percentage volume fraction or weight fraction of a cured composite.
FIBER DIRECTION - The orientation or alignment of the longitudinal axis of
the fiber with respect to a stated reference axis.
FIBERGLASS - The generic name for glass fibers and for composites using
glass fibers for reinforcement.
FIBER REINFORCED PLASTIC - See “Fiber Reinforced Polymer.”
FIBER REINFORCED POLYMER - An engineered material consisting of
reinforcement fibers, polymer resin, and additives to achieve targeted performance
properties. This combination creates an extremely strong and durable material that
can be used for applications ranging from equipment parts to large infrastructure
components.
FIBER SYSTEM - The type and arrangement of fibrous material which
comprises the fiber constituent of an advanced composite. Examples of fiber systems
are collimated filaments or filament yarns, woven fabric, randomly oriented shortfiber ribbons, random fiber mats, whiskers, etc.
FIBER TOW - A loose, untwisted bundle of continuous fibers. In composite
technology, “tow” is often used interchangeably with “yarn”, the twisted version.
FIBER VOLUME - The volume percent of fiber in a composite.
FIBERGLASS - Created by spinning glass as it melts to turn it into glass fibers.
Though sometimes used on its own as a standalone material, fiberglass is a critical
component of Fiber Reinforced Polymers.
FILAMENT - Fibers characterized by extreme length, such that there are
normally no filament ends within a part except at geometric discontinuities. Filaments are used in filamentary composites and are also used in filament winding
processes which require long continuous strands.
FILAMENT COMPOSITES - A major form of advanced composites in which
the fiber constituent consists of continuous filaments. Specifically, a filamentary composite is a laminate comprised of a number of laminae, each of which
consists of a nonwoven, parallel, uniaxial, planar array of filaments ( or filament
yarn) embedded in the selected matrix material. Individual laminae are directionally oriented and combined into specific multi-axial laminates for application to
specific envelopes of strength and stiffness requirements.
ANNEX A: TERMINOLOGY USED WITH NM FRP PULTRUDED COMPONENTS115
FILAMENT WINDING - An automated process in which continuous filament
(or tape) is treated with resin and wound on a removable mandrel in a prescribed
pattern.
FILAMENT WOUND - Pertaining to an object created by the filament winding
method of fabrication.
FILL - Yarn oriented at right angles to the warp in a woven fabric.
FINISH (OR SIZE SYSTEM) - A material, with which filaments are treated,
which contains a coupling agent to improve the bond between the filament surface
and the resin matrix in a composite material. In addition, finishes often contain
ingredients which provide lubricity to the filament surface, preventing abrasive
damage during handling, and a binder which promotes strand integrity and facilitates packing of the filaments.
FLAME-SPRAYED TAPE - A form of metal matrix preply in which the fiber
system is held in place on a foil sheet of matrix alloy by a metallic flamespray
deposit. Each flame-sprayed preply is usually combined in the layup stack with a
metal cover foil and/or additional metal powder to ensure complete encapsulation
of the fibers. During consolidation, all the metallic constituents are coalesced into
a homogeneous matrix.
FLASH - Excess material which forms at the parting line of a mold or die, or
which is extruded from a closed mold.
FRACTURE DUCTILITY - The true plastic strain at fracture.
FRP PANELS - Panels used to build lightweight structures, such as walls and
containers. Specialized combinations of fiber and polymers can create ballistic
panels.
G
GAGE LENGTH - The original length of that portion of the specimen over
which strain or change of length is determined.
GEL - The initial jelly-like solid phase that develops during formation of a resin
from a liquid. Also, a semi-solid system consisting of a network of solid aggregates
in which liquid is held.
GELCOAT - A resin applied to the mold to provide an improved surface for the
composite.
GEL POINT - The stage at which a liquid begins to exhibit pseudo-elastic properties. (This can be seen from the inflection point on a viscosity-time plot.)
GEL TIME - The period of time from a pre-determined starting point to the
onset of gelation (gel point) as defined by a specific test method.
GLASS - An inorganic product of fusion which has cooled to a rigid condition
without crystallizing. In the handbook, all reference to glass will be to the fibrous
form as used in filaments, woven fabric, yarns, mats, chopped fibers, etc.
GLASS CLOTH - Conventionally-woven glass fiber material (see Scrim).
GLASS FIBERS - A fiber spun from an inorganic product of fusion which has
cooled to a rigid condition without crystallizing.
GLASS TRANSITION - The reversible change in an amorphous polymer or
in amorphous regions of a partially crystalline polymer from (or to) a viscous or
rubber condition to (or from) a hard and relatively brittle one.
GLASS TRANSITION TEMPERATURE (Tg) - One method of describing the
temperature at which increased molecular mobility results in significant changes
in the properties of a cured resin system. The glass transition temperature (Tg) can
be defined as the inflection point on a plot of modulus vs. temperature. Another
definition is the intersection point of the coefficient of thermal expansion slopes
below and above Tg (i.e., in the “glassy” region and in the “ rubbery/leathery”
region). Tg is defined as the inflection point; properties can decrease significantly
before Tg is reached.
GRAPHITE - The crystalline, allotropic form of carbon. In bulk form, used
for advanced composite tooling and for such items as the lead in pencils. See
GRAPHITE FIBERS.
116
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
GRAPHITE FIBERS - Technically, a highly oriented form of graphite. In
common usage, however, it also includes highly oriented carbon fibers which have
only a small amount of graphite content.
GRAPHITE FIBERS - See Carbon Fibers.
GRAPHITIZATION - Conversion of carbon to its crystalline allotropic form
by use of very high temperatures (2500 - 4500° F). Diamond is also a crystallizing
allotropic form of carbon, but requires extremely high pressures (over one million
psi) in addition to very high temperatures in order to be formed.
H
HARDENER - The component which reacts with a resin to form the crosslinked (thermoset) plastic.
HARDNESS - Resistance to deformation; usually measured by indention. Types
of standard tests include Brinell, Rockwell, Knoop, and Vickers.
HEAT DISTORTION TEMPERATURE (HDT) - A measure of the softening
point of a material. For unreinforced materials, HDT correlates reasonably well
with the glass transition temperature. The test consists of applying a load to a
specimen in flexure and slowly increasing the temperature until the bar deflects
0.010 inch. HDT is normally reported for stress levels of 66 PSI and/or 264 PSI.
Because the stress levels are so low, HDT is not a particularly useful number for
continuously reinforced materials that will be used at high stress levels.
HETEROGENEOUS - Descriptive term for a material consisting of dissimilar
constituents separately identifiable; a medium consisting of regions of unlike properties separated by internal boundaries. (Note that all nonhomogeneous materials
are not necessarily heterogeneous).
HOMOGENEOUS - Descriptive term for a material of uniform composition
throughout; a medium which has no internal physical boundaries; material whose
properties are constant at every point, i.e.. constant with respect to spatial coordinates (but not necessarily with respect to directional coordinates).
HUMIDITY, RELATIVE - The ratio of the pressure of water vapor present to
the pressure of saturated water vapor at the same temperature.
HYBRID - A composite laminate comprised of laminae of two or more
composite material systems. Or, a combination of two or more different fibers such
as carbon and glass or carbon and aramid into a structure (tapes, fabrics and other
forms may be combined).
HYGROSCOPIC - Capable of absorbing and retaining atmospheric moisture.
HYSTERESIS - The energy absorbed in a complete cycle of loading and
unloading.
I
INCLUSION - A physical and mechanical discontinuity occurring within a
material or part, usually consisting of solid, encapsulated foreign material. Inclusions are often capable of transmitting some structural stresses and energy fields,
but in a noticeably different manner from the parent material.
INTEGRAL COMPOSITE STRUCTURE - Composite structure in which
several structural elements, which would conventionally be assembled by bonding
or with mechanical fasteners after separate fabrication, are instead laid up and
cured as a single, complex, continuous structure: e.g. spars, ribs, and the stiffened
cover of a wing box fabricated as a single integral part. The term is sometimes
applied more loosely to any composite structure not assembled by mechanical
fasteners.
INTEGRALLY HEATED - Referring to tooling which is self-heating through
use of electrical heaters, such as cal rods. Most hydroclave tooling is integrally
heated; some autoclave tooling is integrally heated to compensate for thick sections,
to provide higher heatup rates, or to permit processing at a higher temperature than
the capability of the autoclave.
INTERFACE - The boundary between the individual, physically distinguishable constituents of a composite.
ANNEX A: TERMINOLOGY USED WITH NM FRP PULTRUDED COMPONENTS117
INTERLAMINAR - Descriptive term pertaining to the location of some object
(e.g., voids), event (e.g., fracture), or potential field (e.g., shear stress) referenced
as existing or occurring between two or more adjacent laminae.
INTERLAMINAR SHEAR - Shearing force tending to produce a relative
displacement between two laminae in a laminate along the plane of their interface.
INTRALAMINAR - Descriptive term pertaining to the location of some object
(e.g., voids), event (e.g., fracture), or potential field (e.g., shear stress) referenced
as existing or occurring within a single lamina.
ISOTROPIC - Having uniform properties in all directions. The measured properties of an isotropic material are independent of the axis of testing.
J
K
KEVLAR - An organic polymer composed of aromatic polyamides having
a parallel type orientation. (Parallel chain extending bonds from each aromatic
nucleus).
L
LAMINA -- A single ply or layer in a laminate.
LAMINAE - Plural of lamina.
LAMINATE - A product made by bonding together two or more layers of
laminae of material or materials.
LAMINATE ORIENTATION - The configuration of a crossplied composite
laminate with regard to the angles of crossplying, the number of laminae at each
angle, and the exact sequence of the lamina lay-up.
LAY-UP - A process of fabrication involving the assembly of successive layers
of resin impregnated material.
M
MACRO -- In relation to composites, denotes the gross properties of a composite
as a structural element but does not consider the individual properties or identity
of the constituents.
MACROSTRAIN - The mean strain over any finite gage length of measurement which is large in comparison to the material’s interatomic distance.
MANDREL - A form fixture or male mold used for the base in the production
of a part by layup or filament winding.
MATCHED DIE - A mold, in two or more pieces, which is capable of producing
parts with two or more dimensionally controlled surfaces.
MATERIAL SYSTEM - A specific composite material made from specifically
identified constituents in specific geometric proportions and arrangements and
possessed of numerically defined properties.
MATRIX - The essentially homogeneous material in which the fiber system of
a composite is embedded.
MECHANICAL PROPERTIES - The properties of a material that are associated with elastic and inelastic reaction when force is applied, or the properties
involving the relationship between stress and strain.
MELTING RANGE - Thermoplastics whose makeup includes a distribution of
molecular weights will not have a well defined melting point, but have a melting
range.
MICRO - In relation to composites, denotes the properties of the constituents,
i.e., matrix and reinforcement and interface only, as well as their effects on the
composite properties.
MICROCRACKING - Microcracks are formed in composites when residual
thermal stresses locally exceed the strength of the matrix. Since most microcracks
do not penetrate the reinforcing fibers, microcracks in a crossplied tape laminate
or in a laminate made from cloth prepreg are usually limited to the thickness of a
single ply.
118
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
MICROSTRAIN - The strain over a gage length comparable to the material’s
interatomic distance.
MODULUS, INITIAL - The slope of the initial straight portion of a stressstrain or load-elongation curve.
MODULUS, SECANT - The ratio of change in stress to change in strain
between two points on a stress-strain curve, particularly the points of zero stress
and stress at a particular strain.
MODULUS, TANGENT - The ratio of change in stress to change in strain
derived from the tangent to any point on a stress-strain curve.
MODULUS, YOUNG’S - The ratio of change in stress to change in strain below
the elastic limit of a material. (Applicable to tension and compression).
MODULUS OF RIGIDITY (ALSO SHEAR MODULUS OR TORSIONAL
MODULUS) - The ratio of stress to strain below the proportional limit for shear
or torsional stress.
MOISTURE CONTENT - The amount of moisture in a material determined
under prescribed conditions and expressed as a percentage of the mass of the moist
specimen; i.e., the mass of the dry substance plus the moisture present.
MOISTURE EQUILIBRIUM - The condition reached by a sample when
it no longer takes up moisture from, or gives up moisture to, the surrounding
environment.
MOLDING - The forming of a composite into a prescribed shape by the application of pressure during the cure cycle of the matrix.
N
NDE - Nondestructive Evaluation. Broadly considered synonymous with NDI.
NDI - Nondestructive Inspection. A process or procedure for determining the
quality or characteristics of a material, part, or assembly without permanently
altering the subject or its properties.
NDT - Nondestructive Testing. Broadly considered synonymous with NDI.
NECKING - A localized reduction in cross-sectional area usually due to plastic
deformation which may occur in a material under tensile stress.
NOMINAL SPECIMEN THICKNESS - The nominal ply thickness multiplied
by the number of plies.
NORMALIZED STRESS - Stress calculated by multiplying the raw stress
value by the ratio of measured fiber volume to the nominal fiber volume. This
ratio is often approximated by the ratio of the measured specimen thickness to the
nominal specimen thickness. Stresses for fiber-dominated failure modes are often
normalized.
O
ORTHOTROPIC - Having three mutually perpendicular planes of elastic
symmetry.
OVEN DRY - The condition of a material that has been heated under prescribed
conditions of temperature and humidity until there is no further significant change
in its mass.
P
PAN - Polyacrylonitrile, used in fiber form as a precursor for making carbon/
graphite fibers.
PHENOLIC - Any of several types of synthetic thermosetting resins obtained
by the condensation of phenol or substituted phenols with aldehydes such as
formaldehyde..
PITCH FIBERS - Fibers derived from a special petroleum pitch.
PITCH - High molecular weight material left as a resin after processing of
petroleum (crude oil). After further purification, can be processed into fiber form;
useful as a precursor for production of carbon/graphite fibers.
PLAIN WEAVE - A weaving pattern where the warp and fill fibers alternate;
i.e., the repeat pattern is warp/fill/warp. Both faces of a plain weave are iden-
ANNEX A: TERMINOLOGY USED WITH NM FRP PULTRUDED COMPONENTS119
tical. Properties are significantly reduced relative to a weaving pattern with fewer
crossovers.
PLASTIC - A material that contains one or more organic polymers of large
molecular weight, is solid in its finished state, and, at some state in its manufacture
or processing into finished articles, can be shaped by flow.
PLY - A single layer of prepreg. Used synonymously with LAMINA.
POISSON’S RATIO - The absolute value of the ratio of transverse strain to
corresponding axial strain resulting from uniformly distributed axial stress.
POLYMER - An organic material composed of long molecular chains consisting
of repeating chemical units. Also see RESIN.
POROSITY - A condition of trapped pockets of air, gas, or voids within a cured
laminate, usually expressed as a percentage of the total non-solid volume to the
total volume (solid + non-solid) of a unit quantity of material. See VOID.
POSTCURE - Additional elevated temperature cure, usually without pressure,
to improve final properties or complete the cure or both.
POT LIFE - The period of time during which a reacting thermosetting composition remains suitable for its intended processing after mixing with a reaction initiating agent.
PRECURSOR - In carbon/graphite fiber technology, the organic fiber which is
the starting point for making carbon or graphite fibers. In resin technology, sometimes used to describe the polymers present at an intermediate stage in the formulation of a cured resin.
PREMOLDING - The layup and partial cure at an intermediate cure temperature of a laminated or chopped fiber detail part to stabilize its configuration for
handling and assembly with other parts for final cure.
PRESSURE - The force or load per unit area
PRESSURE INTENSIFIER - A layer of flexible material (usually a high
temperature rubber) used to assure that sufficient pressure is applied to a location,
such as a radius, in a lay-up being cured.
PROPORTIONAL LIMIT - The maximum stress that a material is capable of
sustaining without any deviation from the proportionality of stress to strain (also
known as Hooke’s law).
PULTRUDED FIBERGLASS GRATING - Created using profiles that are
created through a pultrusion process. Pultruded profiles are then assembled into
grates. The pultrusion process produces less waste than molding.
PULTRUSION - A process to continuously process structural shapes or flat
sheet by drawing prepreg materials through forming dies to produce the desired
constant cross sectional shape while simultaneously curing the resin.
Q
QUASI-ISOTROPIC LAMINATE - A laminate approximating isotropy with
equal amounts of plies oriented in several directions.
R
REDUCTION OF AREA - The difference between the original cross sectional
area of a tension test specimen and the area of its smallest cross section, usually
expressed as a percentage of the original area.
REINFORCED PLASTIC - A plastic with relatively high stiffness or very
high strength fibers embedded in the composition. This improves some mechanical
properties over that of the base resin.
REINFORCEMENT - Specialized fibers incorporated into FRP materials to
impart additional characteristics. Typical reinforcement fibers include aramid,
carbon, glass, polyester, and some natural fibers.
RELEASE AGENT - See Mold Release Agent.
RELEASE FILM - An impermeable layer of film which does not bond to the
resin being cured. See SEPARATOR.
RESIN - A form of plastics/polymers commonly used in manufacturing. In FRP,
resins provide the polymer component of Fiber Reinforced Polymer. The resin
120
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
choice largely determines the properties of the FRP product. Most resins used in
FRP are some type of thermoset.
RESIN CONTENT - The amount of matrix present in a composite either by
percent weight or percent volume.
RESIN RICHNESS - An area of excess resin, usually occurring at radii, steps,
and the chamfered edge of core.
RESIN STARVED - An area deficient in resin usually characterized by excess
voids and/or loose fibers.
RESIN SYSTEM - A mixture of resin, with ingredients such as catalyst, initiator, diluents, etc. required for the intended processing and final product. S-BASIS
(OR S-VALUE) -- The mechanical property value which is usually the specified
minimum value of the appropriate government specification or SAE Aerospace
Material Specification for this material.
ROVING - A number of strands, tows, or ends collected into a parallel bundle
with little or no twist.
RUBBER - Crosslinked polymers whose glass transition temperature is below
room temperature and which exhibit highly elastic deformation and have high
elongation.
S
SANDWICH CONSTRUCTION - A structural panel consisting in its simplest
form of two relatively thin, parallel sheets of structural material (face sheets)
bonded to and separated by a relatively thick, lightweight core.
SATURATION -- An equilibrium condition in which the net rate of absorption
under prescribed conditions falls essentially to zero.
SECONDARY BONDING - The joining together, by the process of adhesive
bonding, of two or more already cured composite parts.
SEMI-CRYSTALLINE - In plastics, refers to materials which exhibit localized
crystallinity. See CRYSTALLINITY.
SEPARATOR - A permeable layer which also acts as a release film. Porous
Teflon-coated fiberglass is an example. Often placed between lay-up and bleeder to
facilitate bleeder system removal from laminate after cure.
SET - The strain remaining after complete release of the force producing .The
deformation.
SHEAR FRACTURE (FOR CRYSTALLINE TYPE MATERIALS) - A mode
of fracture resulting from translation along slip planes which are preferentially
oriented in the direction of the shearing stress.
SHELF LIFE - The length of time a material, substance, product, or reagent can
be stored under specified environmental conditions and continue to meet all applicable specification requirements and/or remain suitable for its intended function.
SIZE SYSTEM - See Finish.
SLENDERNESS RATIO - The unsupported effective length of a uniform
column divided by the least radius of gyration of the cross-sectional area.
SLIVER - A continuous strand of loosely assembled fiber that is approximately
uniform in cross-sectional area and has no twist.
SPECIFIC GRAVITY - The ratio of the weight of any volume of a substance to
the weight of an equal volume of another substance taken as standard at a constant
or stated temperature. Solids and liquids are usually compared with water at 4°C
(39°F).
SPECIMEN - A piece or portion of a sample or other material taken to be tested.
Specimens normally are prepared to conform with the applicable test method.
STAGING - Heating a premixed resin system, such as in a prepreg, until the
chemical reaction (curing) starts, but stopping the reaction before the gel point is
reached. Staging is often used to reduce resin flow in subsequent press molding
operation.
ANNEX A: TERMINOLOGY USED WITH NM FRP PULTRUDED COMPONENTS121
STOPS - Metal pieces inserted between die halves; used to control the thickness
of a press molded part. Not a recommended practice, since the resin will end up
with less pressure on it and voids can result.
STRAIN - the per unit change, due to force, in the size or shape of a body
referred to its original size or shape. Strain is a non-dimensional quantity, but it is
frequently expressed in inches per inch, meters per meter, or percent.
STRAND - Normally an untwisted bundle or assembly of continuous filaments
used as a unit, including slivers, tow, ends, yarn. etc. Sometimes a single fiber or
filament is called a strand.
STRENGTH - the maximum stress which a material is capable of sustaining.
STRESS - The intensity at a point in a body of the forces or components of
forces that act on a given plane through the point. Stress is expressed in force per
unit area (pounds-force per square inch, megapascals, etc.).
STRESS RELAXATION - The time dependent decrease in stress in a solid
under given constraint conditions.
STRESS-STRAIN CURVE (DIAGRAM) - A graphical representation showing
the relationship between the change in dimension of the specimen in the direction
of the externally applied stress and the magnitude of the applied stress. Values
of stress usually are plotted as ordinates (vertically) and strain values as abscissa
(horizontally).
SURFACING MAT - A thin mat of fine fibers used primarily to produce a
smooth surface on an organic matrix composite.
SYMMETRICAL LAMINATE - A composite laminate in which the sequence
of plies below the laminate midplane is a mirror image of the stacking sequence
above the midplane.
T
TACKING - To locally join together layers of thermoplastics by localized
melting of the resin. (Also known as Tack Welding).
TAPE - Prepreg fabricated in widths up to 12 inches wide for carbon and 3
inches for boron. Cross stitched carbon tapes up to 60 inches wide are available
commercially in some cases.
THERMAL CONDUCTIVITY - Ability of a material to conduct heat. The
physical constant for quantity of heat that passes through unit cube of a substance
in unit time when the difference in temperature of two faces is one degree.
THERMOPLASTIC - A plastic that repeatedly can be softened by heating and
hardened by cooling through a temperature range characteristic of the plastic; in
the softened stage, it can be shaped by flow into articles by molding or extrusion.
THERMOSET - A plastic that is substantially infusible and insoluble after
having been cured by heat or other means.
TOLERANCE LIMIT - A lower (upper) confidence limit on a specified percentile of a distribution. For example, the B-basis value is a 95% lower confidence
limit on the tenth percentile of a distribution.
TOLERANCE LIMIT FACTOR - The factor which is multiplied by the estimate of variability in computing the tolerance limit.
TOUGHNESS - A measure of a material’s ability to absorb work, or the actual
work per unit volume or unit mass of material that is required to rupture it. Toughness is proportional to the area under the load-elongation curve from the origin to
the breaking point.
TRACER - A fiber, tow or yarn added to a prepreg for verifying fiber alignment
and, in the case of woven materials, distinguishing warp fibers from fill fibers.
TRANSFORMATION - A transformation of data values is a change in the
units of measurement accomplished by applying a mathematical function to all
data values. For example, if the data is given by x, then y - x + 1, x2, l/x, log x, and
cos x are transformations.
TRANSVERSELY ISOTROPIC - Descriptive term for a material exhibiting
a special case of orthotropy in which properties are identical in two orthotropic
122
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
dimensions. but not the third: having identical properties in both transverse directions but not the longitudinal direction.
U
UNBOND - An area within a bonded interface between two adherends in which
the intended bonding action failed to take place. Also used to denote specific areas
deliberately prevented from bonding in order to simulate a defective bond, such as
in the generation of quality standards specimens. (See Disbond, Debond).
UNIDIRECTIONAL LAMINATE - A laminate with non-woven reinforcements and all layers laid up in the same direction.
V
VISCOSITY - the property of resistance to flow exhibited within the body of a
material.
VOID - A physical and mechanical discontinuity occurring within a material or
part which may be 2-D (e.g., disbonds, delaminations) or 3-D (e.g., vacuum-, air-,
or gas-filled pockets). Porosity is an aggregation of micro-voids. Voids are essentially incapable of transmitting structural stresses or non-radiative energy fields .
See INCLUSION.
VOLATILES - Refers to gaseous materials leaving a laminate that is being
cured, and which were liquids or solids before the cure cycle started. Volatiles
produced usually include residual solvents and absorbed or adsorbed water. Many
materials also produce volatiles as by-products of the curing reactions.
W
WET LAY-UP - A method of making a reinforced product by applying a liquid
resin system while the reinforcement is put in place.
WET STRENGTH - The strength of an organic matrix composite after the
composite has absorbed moisture.
WET WINDING - A method of filament winding in which the fiber reinforcement is coated with the resin system as a liquid just prior to wrapping on a mandrel.
WHISKER - A short single fiber or filament. Whisker diameters range from 1 to
25 microns with length-to-diameter ratios between 100 and 15,000.
WORK LIFE - The period during which a compound, after mixing with a catalyst, solvent, or other compounding ingredients, remains suitable for its intended
use.
WOVEN FABRIC COMPOSITE - A major form of advanced composites in
which the fiber constituent consists of woven fabric. A woven fabric composite
normally is a laminate comprised of a number of laminae, each of which consists
of one layer of fabric embedded in the selected matrix material. Individual fabric
laminae are directionally oriented and combined into specific multi-axial laminates
for application to specific envelopes of strength and stiffness requirements.
X
Y
YARN - Generic term for strands of fibers or filaments in a form suitable for
weaving or otherwise intertwining to form a fabric.
YARN, PLIED - Yarns made by collecting two or more single yarns together.
Normally, the yarns are twisted together though sometimes they are collected
without twist.
YIELD STRENGTH - The stress at which a material exhibits a specified
limiting deviation from the proportionality of stress to strain.
Z
ZERO BLEED - A laminate fabrication procedure which does not allow loss of
resin during cure. Also describes prepreg made with the amount of resin desired in
the final part, such that no resin has to be removed during cure.
ANNEX B: PROPERTIES OF COMMERCIALLY AVAILABLE NM FRP PULTRUDED COMPONENTS123
ANNEX B: PROPERTIES OF COMMERCIALLY AVAILABLE NM FRP PULTRUDED COMPONENTS
Company name
Creative Composites Group; dba Creative Pultrusions, Inc.
214 Industrial Lane, Alum Bank, PA 15521
Company Address
Company Website
www.creativecompositesgroup.com
Contact Person
Dustin Troutman
Company Phone
(814) 839-4186
Phone
(814) 285-6824
Company Email
ccg@pultrude.com
info@creativecompositesgroup.com
Email
dtroutman@pultrude.com
Company name
STRONGWELL®
Company Address
400 Commonwealth Ave, Bristol, VA 24201
Company Website
www.strongwell.com
Contact Person
Bhyrav Mutnuri
Company Phone
276 645 8000
Phone
276 645 8078
Company Email
info@strongwell.com
Email
bmutnuri@strongwell.com
124
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Pultex® Equal Leg Angles
Part
Number
Thick-
X-X axis or Y-Y axis
Depth(h)
Width(b)
ness(t)
Area
Weight
I
S
r
rz
in
in
in
in2
lb/ft
in4
in3
in
in
AE120
1
1
0.125
0.22
0.19
0.021
0.030
0.304
0.182
AE140
1
1
0.25
0.42
0.20
0.035
0.053
0.286
0.183
AE122
1.5
1.5
0.125
0.35
0.29
0.075
0.071
0.465
0.284
AE130
1.5
1.5
0.1875
0.51
0.43
0.106
0.101
0.455
0.282
AE142
1.5
1.5
0.25
0.67
0.56
0.133
0.129
0.445
0.281
AE220
2
2
0.125
0.47
0.39
0.186
0.129
0.626
0.386
AE230
2
2
0.1875
0.7
0.55
0.266
0.187
0.616
0.383
AE240
2
2
0.25
0.92
0.71
0.338
0.241
0.606
0.381
AE320
3
3
0.125
0.72
0.59
0.651
0.297
0.949
0.590
AE330
3
3
0.1875
1.08
0.86
0.947
0.435
0.938
0.587
AE340
3
3
0.25
1.42
1.17
1.223
0.568
0.927
0.584
AE360
3
3
0.375
2.09
1.81
1.721
0.815
0.908
0.578
AE440
4
4
0.25
1.92
1.56
3.002
1.034
1.250
0.787
AE460
4
4
0.375
2.84
2.32
4.290
1.499
1.230
0.780
AE480
4
4
0.5
3.72
3.15
5.451
1.934
1.211
0.774
AE640
6
6
0.25
2.92
2.38
10.491
2.382
1.895
1.194
AE660
6
6
0.375
4.34
3.57
15.230
3.492
1.874
1.185
AE680
6
6
0.5
5.72
4.74
19.654
4.552
1.854
1.177
ANNEX B: PROPERTIES OF COMMERCIALLY AVAILABLE NM FRP PULTRUDED COMPONENTS125
Extren® Equal Leg Angles
126
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Pultex® Square Tubes
Part
Width or
Number
Depth(h)
Thickness(t)
Area
Weight
I
X-X axis or Y-Y axis
in
in
2
in
TQ120
1.00
0.125
TQ140
1.25
TQ124
S
r
lb/ft
4
in
3
in
in
0.42
0.34
0.05
0.11
0.36
0.250
0.93
0.76
0.16
0.26
0.42
1.50
0.125
0.67
0.55
0.21
0.28
0.56
TQ142
1.50
0.250
1.24
1.02
0.33
0.44
0.52
TQ126
1.75
0.125
0.80
0.56
0.35
0.40
0.66
TQ144
1.75
0.250
1.48
1.12
0.57
0.67
0.62
TQ220
2.00
0.125
0.92
0.73
0.53
0.53
0.76
TQ230
2.11
0.190
1.44
1.23
0.89
0.84
0.78
TQ240
2.00
0.250
1.73
1.50
0.89
0.89
0.72
TQ242
2.50
0.250
2.24
1.79
1.90
1.52
0.92
TQ247
2.47
0.220
1.97
1.53
1.67
1.35
0.92
TQ340
3.00
0.250
2.74
2.22
3.47
2.31
1.13
TQ440
4.00
0.250
3.73
3.10
8.75
4.37
1.53
CT045
5.20
0.375
7.00
5.99
26.73
10.28
1.95
TQ660
6.00
0.375
8.48
7.58
44.93
14.98
2.30
ANNEX B: PROPERTIES OF COMMERCIALLY AVAILABLE NM FRP PULTRUDED COMPONENTS127
EXTREN® Square Tubes
128
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Pultex® Round Tubes
Part
Outside
Inside
X-X axis
Number
Diameter (D)
Diameter (d)
in
in
in
in2
lb/ft
in4
in3
in
TU005
0.75
0.56
0.09
0.19
0.16
0.01
0.03
0.23
TU120
1.00
0.75
0.13
0.34
0.23
0.03
0.07
0.31
TU122
1.25
1.00
0.13
0.44
0.75
0.07
0.11
0.40
Thickness(t)
Area
Weight
I
S
r
TU118
1.25
1.00
0.09
0.34
0.34
0.06
0.09
0.41
TU143
1.50
1.00
0.25
0.98
0.46
0.20
0.27
0.45
TU124
1.50
1.25
0.13
0.54
0.82
0.13
0.17
0.49
TU142
1.75
1.25
0.25
0.91
0.5
0.34
0.39
0.54
TU126
1.75
1.50
0.13
0.64
0.94
0.21
0.24
0.58
TU240
2.00
1.50
0.25
1.37
0.59
0.54
0.54
0.63
TU220
2.00
1.75
0.13
0.73
1.15
0.33
0.33
0.66
TU242
2.50
2.00
0.25
1.77
0.71
1.13
0.91
0.80
TU222
2.50
2.25
0.13
0.93
1.35
0.66
0.53
0.84
TU320
3.00
2.75
0.13
1.13
0.92
1.17
0.78
1.02
TU340
3.00
2.50
0.25
2.16
1.71
2.06
1.37
0.98
TU410
4.02
3.46
0.28
3.24
2.79
5.69
2.84
1.33
ANNEX B: PROPERTIES OF COMMERCIALLY AVAILABLE NM FRP PULTRUDED COMPONENTS129
EXTREN® Round Tubes
130
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Pultex® Wide Flange Sections
Depth (h)
Width(b)
Thickness (t)
Area
Weight
I
in
in
in
2
in
IW340
3
3
0.25
IW440
4
4
IW640
6
6
IW660
6
IW860
8
Part Number
X-X axis
Y-Y axis
S
r
I
lb/ft
4
in
3
in
2.17
1.85
3.23
0.25
2.92
2.86
0.25
4.42
3.83
6
0.375
6.57
5.79
8
0.375
8.82
Design
S
r
J
in
4
in
3
in
2.15
1.22
1.11
8.05
4.03
1.66
28.58
9.53
2.54
40.76
13.59
7.77
100.35
Cw
in
4
in
in6
0.74
0.71
0.047
2.49
2.63
1.32
0.95
0.063
10.52
8.91
4.46
1.42
0.094
80.21
2.49
13.32
4.44
1.42
0.316
119.84
25.09
3.37
31.65
7.91
1.9
0.422
506.46
IW880
8
8
0.5
11.67
10.39
128.81
32.2
3.32
42.09
10.52
1.9
1.000
673.41
IW960
10
10
0.375
11.07
9.59
200.45
40.09
4.26
61.94
12.39
2.37
0.527
1548.59
IW980
10
10
0.5
14.67
12.92
259.36
51.87
4.2
82.38
16.48
2.37
1.250
2059.52
IW982
12
12
0.5
17.67
16.65
457.26
76.21
5.09
142.59
23.77
2.84
1.500
5133.35
Depth(h)
Width(b)
Thickness
(t)
Area
Weight
I
S
r
I
S
r
J
in
in
in
2
in
lb/ft
4
in
3
in
in
4
in
3
in
IB340
3
1.5
0.25
1.42
1.22
1.803
1.202
1.178
0.140
IB440
4
2
0.25
1.92
1.65
4.530
2.265
1.537
IB640
6
3
0.25
2.92
2.49
16.170
5.390
IB660
6
3
0.375
4.32
3.67
22.930
IB860
8
4
0.375
5.82
5.17
IB880
8
4
0.5
7.67
IB960
10
5
0.375
IB980
10
5
IB982
12
6
Pultex® I-Sections
Part
Number
X-X axis
Y-Y axis
Design
Cw
in
4
in
in6
0.186
0.314
0.031
0.315
0.329
0.329
0.414
0.042
1.316
2.350
1.110
0.740
0.620
0.063
9.990
7.640
2.310
1.670
1.110
0.620
0.211
15.000
56.710
14.180
3.120
3.950
1.970
0.820
0.281
63.120
6.81
72.480
18.120
3.070
5.270
2.630
0.820
0.667
84.260
7.32
6.43
113.550
22.710
3.940
7.710
3.080
1.030
0.352
192.800
0.5
9.67
8.51
146.450
29.290
3.890
10.270
4.110
1.030
0.833
256.840
0.5
11.67
10.31
258.760
43.130
4.710
17.760
5.920
1.230
1.000
639.330
ANNEX B: PROPERTIES OF COMMERCIALLY AVAILABLE NM FRP PULTRUDED COMPONENTS131
Extren® I-Shapes
132
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Pultex® Rectangular Tubes
Part
X-X axis
Y-Y axis
S
r
in
4
in
3
in
in
0.083
0.300
0.059
0.101
0.402
2.89
1.31
1.45
0.49
0.68
0.59
4.20
1.77
1.64
0.79
0.91
0.71
1.38
3.92
1.96
1.50
0.78
0.90
0.67
1.77
1.53
5.75
2.26
1.80
1.20
1.20
0.82
0.125
2.39
1.92
9.34
3.11
1.98
1.61
1.61
0.82
0.25
4.62
3.87
22.31
7.44
2.20
11.84
5.92
1.61
4
0.25
5.2
4.09
33.61
9.61
2.54
13.91
6.95
1.64
7
4
0.375
7.63
6.21
47.58
13.60
2.50
19.25
9.63
1.59
**TR815
8
1
0.125
2.47
1.88
14.47
3.62
2.42
0.41
0.81
0.41
TR842
8
4
0.25
5.7
4.7
46.80
11.70
2.87
15.67
7.83
1.66
TR860
8
4
0.375
8.38
6.71
66.63
16.66
2.82
21.73
10.86
1.61
Number
Depth(h)
Width(b)
Thickness (t)
Area
Weight
I
in
in
in
2
S
r
I
lb/ft
4
in
3
in
in
0.8
1.165
0.11
0.366
0.3
0.033
TR420
4.4
1.43
0.13
TR422
4.74
1.72
0.125
1.38
1.1
1.57
1.36
TR440
4
1.74
0.25
1.74
TR522
5.08
2
0.125
*TR620
TR640
6
2
6
4
TR740
7
TR760
TR120
* Contains internal webs.
** Contains internal webs. Special properties apply, consult CPI.
ANNEX B: PROPERTIES OF COMMERCIALLY AVAILABLE NM FRP PULTRUDED COMPONENTS133
EXTREN® Rectangular Shapes
134
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Pultex® Unequal Leg Angles
Part
Number
Thick-
X-X axis
Y-Y axis
Depth(h)
Width(b)
ness(t)
Area
Weight
I
S
r
I
S
r
in
in
in
in2
lb/ft
in4
in3
in
in4
in3
in
AU122
1.5
1.0
0.125
0.29
0.23
0.065
0.066
0.477
0.024
0.032
0.288
AU220
2.0
1.0
0.125
0.35
0.22
0.144
0.114
0.643
0.026
0.033
0.271
AU230
2.0
1.0
0.1875
0.51
0.40
0.206
0.165
0.633
0.035
0.046
0.262
AU240
2.0
1.0
0.25
0.67
0.53
0.261
0.212
0.623
0.043
0.059
0.254
AU242
2.0
1.3
0.25
0.73
0.36
0.285
0.222
0.623
0.085
0.093
0.340
AU222
2.0
1.5
0.125
0.41
0.58
0.168
0.123
0.640
0.083
0.073
0.449
AU244
2.0
1.5
0.25
0.8
0.37
0.305
0.230
0.619
0.146
0.135
0.429
AU224
2.6
1.6
0.125
0.5
0.63
0.334
0.224
0.715
0.121
0.107
0.429
AU320
3.0
1.0
0.125
0.47
0.39
0.365
0.209
0.851
0.112
0.089
0.472
AU322
3.0
1.5
0.125
0.54
0.57
0.440
0.244
0.964
0.028
0.034
0.243
AU330
3.0
1.5
0.1875
0.8
0.39
0.511
0.264
0.977
0.092
0.077
0.415
AU332
3.0
2.0
0.1875
0.89
0.70
0.957
0.505
0.956
0.164
0.142
0.396
AU342
3.0
2.0
0.25
1.17
0.91
0.825
0.408
0.963
0.301
0.197
0.582
AU360
3.0
2.0
0.375
1.71
1.33
1.064
0.532
0.953
0.383
0.255
0.572
AU440
4.0
2.0
0.25
1.42
1.15
1.493
0.762
0.934
0.526
0.360
0.554
AU460
4.0
2.0
0.375
2.09
1.74
2.362
0.922
1.289
0.413
0.263
0.539
AU442
4.0
3.0
0.25
1.67
1.37
3.359
1.333
1.269
0.568
0.373
0.522
AU462
4.0
3.0
0.375
2.46
2.10
2.730
0.989
1.278
1.335
0.590
0.894
AU580
5.0
3.5
0.50
3.97
2.96
3.894
1.434
1.258
1.882
0.848
0.874
AU660
6.0
4.0
0.375
3.59
3.04
9.183
2.240
1.947
0.378
1.088
1.181
AU680
6.0
4.0
0.50
4.72
3.87
13.311
3.280
1.926
4.835
1.580
1.161
AU961
10.0
5.0
0.375
5.46
4.47
58.286
8.941
3.267
10.435
2.594
1.382
ANNEX B: PROPERTIES OF COMMERCIALLY AVAILABLE NM FRP PULTRUDED COMPONENTS135
Unequal Leg Angle
Pultex® Channels
Part
Number
Depth(h)
Width(b)
Thickness
( t)
X-X axis
Area
Weight
I
2
Y-Y axis
S
r
I
4
3
S
r
in
in
in
in
lb/ft
in
in
in
in
in
in
CH130
1.5
1
0.1875
0.55
0.45
0.166
0.222
0.551
0.048
0.076
0.297
CH222
2
0.56
0.125
0.34
0.3
0.164
0.164
0.692
0.007
0.018
0.147
CH224
2.75
1
0.125
0.56
0.45
0.586
0.426
1.024
0.046
0.061
0.286
CH340
3
0.875
0.25
1
0.81
1.018
0.678
1.011
0.050
0.080
0.223
CH330
3
1
0.1875
0.83
0.72
0.945
0.630
1.069
0.062
0.086
0.275
CH342
3
1.5
0.25
1.31
1.04
1.611
1.074
1.110
0.255
0.248
0.441
CH420
4
1.06
0.125
0.71
0.6
1.456
0.728
1.431
0.060
0.072
0.290
CH434
4
1.75
0.1875
1.1
0.9
2.850
1.425
1.607
0.333
0.275
0.550
CH440
4
1.13
0.25
1.37
1.07
2.628
1.314
1.384
0.118
0.142
0.293
CH450
4.5
2.5
0.25
2.18
1.81
6.666
2.962
1.748
1.294
0.742
0.770
CH540
5
1.38
0.25
1.75
1.4
5.385
2.154
1.756
0.231
0.223
0.364
CH640
6
1.63
0.25
2.12
1.75
9.611
3.204
2.129
0.402
0.323
0.435
CH662
6
1.69
0.375
3.1
2.61
13.427
4.476
2.081
0.621
0.503
0.447
CH740
7
2
0.25
2.57
2.03
16.420
4.692
2.530
0.794
0.517
0.556
CH840
8
2.19
0.25
2.91
2.42
24.300
6.075
2.890
1.068
0.628
0.606
CH860
8
2.19
0.375
4.23
3.57
33.751
8.437
2.826
1.470
0.890
0.590
CH922
10
2.75
0.125
1.88
1.55
25.885
5.177
3.706
1.180
0.534
0.791
CH980
10
2.75
0.5
7.01
5.94
86.876
17.375
3.519
3.828
1.855
0.739
CH995
11.5
2.75
0.5
7.78
6.69
124.581
21.666
4.001
4.054
1.930
0.722
CH990
24
3
0.25
7.33
5.89
475.404
39.617
8.054
3.374
1.300
0.679
CH994
24
4
0.47
14.52
11.88
985.090
82.090
8.237
13.710
4.143
0.972
4
3
136
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Extren® Channels
ANNEX B: PROPERTIES OF COMMERCIALLY AVAILABLE NM FRP PULTRUDED COMPONENTS137
Pultex® Solid Round Rods
X-X axis or Y-Y axis
Round Rod
Diameter(d)
Area
Weight
Part Number
in
in2
lb/ft
SO004
0.25
0.049
0.430
SO006
0.375
0.110
SO008
0.5
0.196
SO010
0.625
SO012
I
S
r
in3
in
<1.00E-03
0.002
0.063
0.940
1.00E-03
0.005
0.094
0.170
3.00E-03
0.012
0.125
0.307
0.270
8.00E-03
0.024
0.156
0.75
0.442
0.390
1.60E-02
0.041
0.188
SO016
1
0.785
0.690
4.90E-02
0.098
0.250
SO020
1.25
1.227
1.070
1.20E-01
0.192
0.313
SO024
1.5
1.767
1.480
2.49E-01
0.331
0.375
SO032
2
3.142
2.750
7.85E-01
0.785
0.500
138
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Pultex® Solid Bars
X-X axis
Y-Y axis
Depth(h)
Width(b)
Area
Weight
I
S
r
I
S
r
in
in
in2
lb/ft
in4
in3
in
in4
in3
in
SQ040
0.25
0.25
0.06
0.050
< .001
0.002
0.070
< .001
0.002
0.070
SQ011
1.00
1.00
0.99
0.850
0.080
0.161
0.285
0.080
0.161
0.285
SQ020
1.23
1.23
1.51
1.280
0.189
0.306
0.354
0.189
0.306
0.354
SQ024
1.46
1.46
2.12
1.800
0.373
0.510
0.419
0.373
0.510
0.419
Part
Number
Square Bars
ANNEX B: PROPERTIES OF COMMERCIALLY AVAILABLE NM FRP PULTRUDED COMPONENTS139
Pultex® Sludge Flights
X-X axis
Depth(h)
Width(b)
Area
Weight
I
in
in
in2
lb/ft
SF011
6
2.5
1.64
SF021
8
2.5
1.87
Part
Number
Structural Tees
Y-Y axis
S
r
I
4
in
3
S
r
in
4
in
3
in
in
in
1.48
7.81
1.68
15.59
2.77
2.18
1.02
0.58
0.79
4.11
2.88
1.11
0.6
0.77
140
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Double EXTREN® Channels
ANNEX B: PROPERTIES OF COMMERCIALLY AVAILABLE NM FRP PULTRUDED COMPONENTS141
Double Angles: EXTREN® Equal Leg Angles
EXTREN® Construction Grade Plate
142
Flat Strips
F Section
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
ANNEX B: PROPERTIES OF COMMERCIALLY AVAILABLE NM FRP PULTRUDED COMPONENTS143
Struts
Kick Plates
144
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
Square Tube / Round Hole
Z Section
Slide Guide
ANNEX B: PROPERTIES OF COMMERCIALLY AVAILABLE NM FRP PULTRUDED COMPONENTS145
Flight channel
Curb Angles
146
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
SAFRAIL™ Post or Rail Section
SAFRAIL™ Round Handrail Post or Rail Section
Half Round Rail Section
ANNEX C: LIST OF PROJECT EXAMPLES 147
ANNEX C: LIST OF PROJECT EXAMPLES
In this annex the curated list of construction project examples provided within
the main document is summarized herein. It’s important to note that this list is not
exhaustive but serves as a representative selection to illustrate the versatility and
efficacy of FRP pultruded materials. These examples are intended to provide a
tangible understanding of how FRP pultruded materials can be effectively utilized
in different contexts. The intent is to keep expanding this list as a reference for FRP
pultruded solutions, as its implementation grows in the built infrastructure.
12.1 GENERAL CONSTRUCTION
12.1.1 Structural Framing
• FRP profiles at the façade of a building on the University College Ghent’s
Schoonmeersen Campus (Ghent, Belgium). 2012.
• FRP framing replaces deteriorated steel framing in trickling filter (Girardeau,
Missouri). 2014.
• FRP temporary shelter located inside a deteriorated church (L’Aquila, Italy).
2010.
• Freestanding CFRP roof at the Apple Campus 2 ‘Theatre’ (Cupertino, California). 2019.
12.1.2 Concrete Reinforcement
• Secant pile seawall behind beach dunes to protect SR A1A (Flagler Beach,
Florida). 2019.
• Jizan Flood Mitigation Channel (Jizan Economic City, Saudi Arabia). 2020.
• BFRP reinforced topping slabs of the Avocet Tower (Bethesda, Maryland).
2021.
• Concrete repair of the Negrelli viaduct in Prague using BFRP mesh (Prague,
Check Reepublic). 2017.
• FRP dowels in new highway Route 219 and Route 33 East (Elkins, West
Virginia). 2002.
• BFRP reinforced concrete retaining wall at the Port of Miami tunnel (Miami,
Florida). 2014.
• Prestressed FRP laminate system for strengthening the Fenghu River bridge
(Shangai, China). 2015.
12.1.3 Cladding and Fenestration
• Fiberglass windows in a residential condo (Gresham, Oregon).
• Opaque composite roof tiles in a warehouse in Port of Salaverry (Salaverry,
Peru). 2022.
12.1.4 Pedestrian Bridges and Boardwalks
• Pedestrian Bridge at Walker Ranch Park (San Antonio, TX). 2006.
• Pedestrian Bridge, Bermuda Railway (Bermuda). 2021
• West Hanover Boardwalk (West Hanover, PA). 2007.
12.1.5 Vehicular Bridge Decks
• Blackfriars Bridge (London, Ontario). 2018.
• Golf Resort Bascule Bridge (Cayman Islands). 2020.
• FRP bridge decking at the Franklin Street bascule bridge (Michigan City,
Indiana). 2019.
12.2 INDUSTRIAL PLANTS
• GFRP components for the magnet support structure of the International
Thermonuclear Experimental Reactor (Saint-Paul-lez-Durance, France). In
progress.
148
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
12.3 TRANSPORTATION
12.3.1 FRP for platform structures
• 45th and Courthouse Square MTA (Queens, NY). 2012
12.3.2 Posts and fences
• Frangible airport fence at Zilina airport (Zilina, Slovakia). 2009.
• Composite fencing for a pacific coastal resort (Pismo Beach, California).
2017.
12.4 WATERFRONT
12.4.1 Fender Systems
• Ravenswood bridge fender system (Dania, Florida). 2017
• Wastewater Baffle and Diffuser Walls (California). 2015.
12.4.2 Sheet Pile Walls
• Laurence Harbor Wastewater Facility Storm Surge Protection wall (New
Jersey, USA)
• United States Navy Pier (Chollas Creek, San Diego, CA). 2005.
12.4.3 Dock and Marinas
• Residential composite pier (Bath, ME). 2010.
12.4.4 Offshore Structures
• Offshore oil platforms using FRP grating (California). 1979.
12.5 UTILITY AND TELECOMUNICATIONS
12.5.1 Utility Poles
• Self-Extinguishing Utility Poles (California, USA)
12.5.2 Cross-Arms
• Fiberglass cross-arms for substation (Johnson City, Tennessee). 2018.
12.5.3 FRP Panels
• Structural insulated panels for refrigerated facility for Hidewood Meats
(Brandt, Minnesota). 2022.
12.5.4 Industrial Tanks & Processing Equipment
• University of Arizona Cooling Tower (Tucson, Arizona). 2008.
• Water Clarifier Tank Covers (Kelowna, British Columbia, Canada). 2000.
• FRP profiles in balconies (Pittsburgh, PA)
ANNEX D: NM FRP PULTRUDED STANDARDS LIST149
ANNEX D: NM FRP PULTRUDED STANDARDS LIST
14.1 Standards and Specifications (per Standard Organization and Type)
American Society of Testing and Materials (ASTM) Test Methods
ASTM STANDARD TEST METHODS
Standard
number
Title
Brief description
D7264
Standard Test Method for Flexural Properties of Polymer Matrix Composite Materials
Flexural strength
D6641
Standard Test Method for Compressive Properties of Polymer Matrix Composite Materials Using a
Combined Loading Compression (CLC) Test Fixture
Compressive strength
D638
Standard Test Method for Tensile Properties of Plastics
Tensile strength
D5766
Standard Test Method for Open-Hole Tensile Strength of Polymer Matrix Composite Laminates
Open-hole tensile strength
D5379
Standard Test Method for Shear Properties of Composite Materials by the V-Notched Beam Method
In-plane shear strength
D5379
Standard Test Method for Shear Properties of Composite Materials by the V-Notched Beam Method
Through-the-thickness shear
D2344
Standard Test Method for Short-Beam Strength of Polymer Matrix Composite Materials and Their
Laminates
Short beam strength
D7332
Standard Test Method for Measuring the Fastener Pull-Through Resistance of a Fiber-Reinforced
Polymer Matrix Composite
Pull-through strength per
fastener
E84
Standard test method for assessing the surface burning characteristics of building materials
Surface burning behavior
D638
Standard Test Method for Tensile Properties of Plastics
Tensile Strength & Modulus
D695
Standard Test Method for Compressive Properties of Rigid Plastics
Compr. Strength & Modulus
D790
Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials
Flexural Strength & Modulus
D5379
Standard Test Method for Shear Properties of Composite Materials by the V-Notched Beam Method
Shear Modulus
D2344
Standard Test Method for Short-Beam Strength of Polymer Matrix Composite Materials and Their
Laminates
Short Beam Shear
D953
Standard Test Method for Pin-Bearing Strength of Plastics
Ultimate Bearing strength
D3039
Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials
Poisson’s Ratio
D256
Standard Test Methods for Determining the Izod Pendulum Impact Resistance of Plastics
Notched Izod Impact
D2583
Standard Test Method for Indentation Hardness of Rigid Plastics by Means of a Barcol Impressor
(Withdrawn 2022)
Barcol Hardness
D570
Standard Test Method for Water Absorption of Plastics
24-hr. Water Absorption
D792
Standard Test Methods for Density and Specific Gravity (Relative Density) of Plastics by
Displacement
Density
D696
Standard Test Method for Coefficient of Linear Thermal Expansion of Plastics Between −30°C and
30°C with a Vitreous Silica Dilatometer
Coeff. of Thermal Expansion
C177
Standard Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the Guarded-Hot-Plate Apparatus
Thermal Conductivity
D495
Standard Test Method for High-Voltage, Low-Current, Dry Arc Resistance of Solid Electrical
Insulation
Arc Resistance
D149
Standard Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical
Insulating Materials at Commercial Power Frequencies
Dielectric Strength
E84
Standard Test Method for Surface Burning Characteristics of Building Materials
Tunnel Test
E662
Standard Test Method for Specific Optical Density of Smoke Generated by Solid Materials
NBS Smoke Chamber
D 3410
Standard Test Method for Compressive Properties of Polymer Matrix Composite Materials with
Unsupported Gage Section by Shear Loading
Longitudinal tensile strength
D 695
Standard Test Method for Compressive Properties of Rigid Plastics
D 5961
Standard Test Method for Bearing Response of Polymer Matrix Composite Laminates
D 953
Standard Test Method for Pin-Bearing Strength of Plastics
Longitudinal compressive strength
150
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
ASTM STANDARD TEST METHODS
Standard
number
Title
Brief description
D 2344
Standard Test Method for Short-Beam Strength of Polymer Matrix Composite Materials and Their
Laminates
D 4475
Standard Test Method for Apparent Horizontal Shear Strength of Pultruded Reinforced Plastic Rods
By the Short-Beam Method
D 5379
Standard Test Method for Shear Properties of Composite Materials by the V-Notched Beam Method
D 3846
Standard Test Method for In-Plane Shear Strength of Reinforced Plastics
Longitudinal short beam shear
strength
D 256
Standard Test Methods for Determining the Izod Pendulum Impact Resistance of Plastics
In-plane shear strength
D 638
Standard Test Method for Tensile Properties of Plastics
D 3039
Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials
D 5083
Standard Test Method for Compressive Properties of Rigid Plastics
D 695
Standard Test Method for Compressive Properties of Rigid Plastics
D 3410
Standard Test Method for Compressive Properties of Polymer Matrix Composite Materials with
Unsupported Gage Section by Shear Loading
Transverse compressive strength
D 2344
Standard Test Method for Short-Beam Strength of Polymer Matrix Composite Materials and Their
Laminates
Transverse short beam shear
strength
D 953
Standard Test Method for Pin-Bearing Strength of Plastics
D 5961
Standard Test Method for Bearing Response of Polymer Matrix Composite Laminates
D3039
Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials
Longitudinal bearing strength
Transverse tensile strength
Transverse bearing strength
D638
Standard Test Method for Tensile Properties of Plastics
D5083
Standard Test Method for Compressive Properties of Rigid Plastics
D3916
Standard Test Method for Tensile Properties of Pultruded Glass-Fiber-Reinforced Plastic Rod
D2584
Standard Test Method for Ignition Loss of Cured Reinforced Resins
D3171
Standard Test Methods for Constituent Content of Composite Materials
D792
Standard Test Methods for Density and Specific Gravity (Relative Density) of Plastics by
Displacement
Density
D 2583
Standard Test Method for Indentation Hardness of Rigid Plastics by Means of a Barcol Impressor
(Withdrawn 2022)
Barcol hardness
E1356
Standard Test Method for Assignment of the Glass Transition Temperatures by Differential Scanning
Calorimetry
E1640
Standard Test Method for Assignment of the Glass Transition Temperature By Dynamic Mechanical
Analysis
D648
Standard Test Method for Deflection Temperature of Plastics Under Flexural Load in the Edgewise
Position
E2092
Standard Test Method for Distortion Temperature in Three-Point Bending by Thermomechanical
Analysis
D570
Standard Test Method for Water Absorption of Plastics
D696
Standard Test Method for Coefficient of Linear Thermal Expansion of Plastics Between −30°C and
30°C with a Vitreous Silica Dilatometer
E831
Standard Test Method for Linear Thermal Expansion of Solid Materials by Thermomechanical
Analysis
D696
Standard Test Method for Coefficient of Linear Thermal Expansion of Plastics Between −30°C and
30°C with a Vitreous Silica Dilatometer
E831
Standard Test Method for Linear Thermal Expansion of Solid Materials by Thermomechanical
Analysis
Longitudinal tensile modulus
Fiber volume fraction
Glass transition temperature
Water absorbed when substantially saturated
Longitudinal coefficient of
thermal expansion
Transverse coefficient of thermal
expansion
ANNEX D: NM FRP PULTRUDED STANDARDS LIST151
ASTM STANDARD TEST METHODS
Standard
number
Title
E84
Standard Test Method for Surface Burning Characteristics of Building Materials
D635
Standard Test Method for Rate of Burning and/or Extent and Time of Burning of Plastics in a Horizontal Position
Brief description
Flammability and smoke
generation
E662
Standard Test Method for Specific Optical Density of Smoke Generated by Solid Materials
D149
Standard Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical
Insulating Materials at Commercial Power Frequencies
D1929
Standard Test Method for Determining Ignition Temperature of Plastics
Flash ignition temperature
Standard Practice for Classifying Failure Modes in Fiber-Reinforced-Plastic (FRP) Joints
Failure mode classification
(Adhesively Bonded)
D5573
D5868
Standard Test Method for Lap Shear Adhesion for Fiber Reinforced Plastic (FRP) Bonding
D3163
Standard Test Method for Determining Strength of Adhesively Bonded Rigid Plastic Lap-Shear
Joints in Shear by Tension Loading
D3164
Standard Test Method for Strength Properties of Adhesively Bonded Plastic Lap-Shear Sandwich
Joints in Shear by Tension Loading
D3165
Standard Test Method for Strength Properties of Adhesives in Shear by Tension Loading of SingleLap-Joint Laminated Assemblies
D2093
Standard Practice for Preparation of Surfaces of Plastics Prior to Adhesive Bonding
D897
Standard Test Method for Tensile Properties of Adhesive Bonds
D2095
Standard Test Method for Tensile Strength of Adhesives by Means of Bar and Rod Specimens
D1781
Standard Test Method for Climbing Drum Peel for Adhesives
D1876
Standard Test Method for Peel Resistance of Adhesives (T-Peel Test)
D3167
Standard Test Method for Floating Roller Peel Resistance of Adhesives
D1184
Standard Test Method for Flexural Strength of Adhesive Bonded Laminated Assemblies
D5041
Standard Test Method for Fracture Strength in Cleavage of Adhesives in Bonded Joints
D950
Standard Test Method for Impact Strength of Adhesive Bonds
D1062
Standard Test Method for Cleavage Strength of Metal-to-Metal Adhesive Bonds
D3433
Standard Test Method for Fracture Strength in Cleavage of Adhesives in Bonded Metal Joints
D1780
Standard Practice for Conducting Creep Tests of Metal-to-Metal Adhesives
D2293
Standard Test Method for Creep Properties of Adhesives in Shear by Compression Loading
(Metal-to-Metal)
D2294
Standard Test Method for Creep Properties of Adhesives in Shear by Tension Loading
(Metal-to-Metal)
D3166
Standard Test Method for Fatigue Properties of Adhesives in Shear by Tension Loading (Metal/
Metal)
D1151
Standard Practice for Effect of Moisture and Temperature on Adhesive Bonds
D1828
Standard Practice for Atmospheric Exposure of Adhesive-Bonded Joints and Structures
D2918
Standard Test Method for Durability Assessment of Adhesive Joints Stressed in Peel
D2919
Standard Test Method for Determining Durability of Adhesive Joints Stressed in Shear by Tension
Loading
D907
Standard Terminology of Adhesives
D4800
Standard Guide for Classifying and Specifying Adhesives
D1084
Standard Test Methods for Viscosity of Adhesives
D7149
Standard Practice for Determining the Freeze Thaw Stability of Adhesives
D2556
Standard Test Method for Apparent Viscosity of Adhesives Having Shear-Rate-Dependent Flow
Properties Using Rotational Viscometry
Dielectric strength
Tensile shear loading (Adhesively Bonded)
Laminate surface preparation
(Adhesively Bonded)
Tensile loading (butt joint)
(Adhesively Bonded)
Peel Loading (Adhesively
Bonded)
Flexural loading (Adhesively
Bonded)
Cleavage loading (Adhesively
Bonded)
Creep (Adhesively Bonded)
Fatigue (Adhesively Bonded)
Durability (Adhesively Bonded)
Standard terminology (Adhesive
Characterization)
Physical properties (Adhesive
Characterization)
152
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
ASTM STANDARD TEST METHODS
Standard
number
Title
Brief description
D3893
Standard Test Method for Purity of Methyl Amyl Ketone and Methyl Isoamyl Ketone by Gas
Chromatography
D4027
Standard Test Method for Measuring Shear Properties of Structural Adhesives by the Modified-Rail
Test
D905
Standard Test Method for Strength Properties of Adhesive Bonds in Shear by Compression Loading
D4896
Standard Guide for Use of Adhesive-Bonded Single Lap-Joint Specimen Test Results
D5868
Standard Test Method for Lap Shear Adhesion for Fiber Reinforced Plastic (FRP) Bonding
Bonding characteristics (Adhesive Characterization)
D1183
Standard Practices for Resistance of Adhesives to Cyclic Laboratory Aging Conditions
Environmental aging (Adhesive
Characterization)
Strength and shear modulus
(Adhesive Characterization)
ASTM STANDARD SPECIFICATIONS
Standard name
Title
D2291
Standard Practice for Fabrication of Ring Test Specimens for Glass-Resin Composites
D3917
Standard Specification for Dimensional Tolerance of Thermosetting Glass-Reinforced Plastic Pultruded Shapes
D7957
Standard Specification for Solid Round Glass Fiber Reinforced Polymer Bars for Concrete Reinforcement
D8505
Standard Specification for Basalt and Glass Fiber Reinforced Polymer (FRP) Bars for
Concrete Reinforcement
D8448
Standard Specification for Basalt Fiber Strands
D578
Standard Specification for Glass Fiber Strands
ASTM STANDARD TERMINOLOGIES
Standard name
C 162
Standard Terminology of Glass and Glass Products
C 904
Standard Terminology Relating to Chemical-Resistant Nonmetallic Materials
D 123
Standard Terminology Relating to Textiles
D 883
Standard Terminology Relating to Plastics
D 907
Standard Terminology of Adhesives
D 3878
Standard Terminology of Composite Materials
D 3918
Standard Terminology Relating to Reinforced Plastic Pultruded Products
E6
Standard Terminology Relating to Methods of Mechanical Testing
E 631
Standard Terminology of Building Constructions
ASTM STANDARD PRACTICES
Standard name
Title
C 581
Standard Practice for Determining Chemical Resistance of Thermosetting Resins Used in Glass-Fiber-Reinforced Structures Intended
for Liquid Service
D 618
Standard Practice for Conditioning Plastics for Testing
E 122
Standard Practice for Calculating Sample Size to Estimate, with a Specified Tolerable Error, the Average for a Characteristic of a Lot
or Process
E 632
Standard Practice for Developing Accelerated Tests to Aid Prediction of the Service Life of Building Components and Materials
ANNEX D: NM FRP PULTRUDED STANDARDS LIST153
CEN 13706 Test Methods for FRP Pultruded Profiles
CEN NORMATIVE TEST METHODS
Standard name
Title
Part 2 Annex A
Part 2 Annex A Visual Defects: Descriptions and Acceptance Levels
Part 2 Annex B
Part 2 Annex B Dimensional Tolerance for Pultruded Profiles
Part 2 Annex C
Part 2 Annex C Workmanship
Part 2 Annex D
Part 2 Annex D Determination of Effective Flexural Modulus
Part 2 Annex E
Part 2 Annex E Determination of the Pin Bearing Strength
CEN INFORMATION TEST METHODS
Standard name
Title
Part 2 Annex F
Recommended Test Methods for Particular Requirements
Part 2 Annex G
Determination of Flexural Shear and Torsional Stiffness Properties
CSA S806 Standard Test Methods for FRP Bars and Laminates
CEN NORMATIVE TEST METHODS
Standard name
Title
Annex A
Determination of Cross-Sectional Area of FRP Reinforcement
Annex B
Anchor for Testing FRP Specimens Under Monotonic, Sustained and Cyclic Tension
Annex C
Test Method for Tensile Properties of FRP Reinforcements
Annex D
Test Method for Development Length of FRP Reinforcement
Annex E
Test Method for FRP Bent Bars and Stirrups
Annex F
Test Method for Direct Tension Pull-off Test
Annex G
Test Method for Tension Test of Flat Specimens
CEN INFORMATION TEST METHODS
Standard name
Title
Annex H
Test Method for Bond Strength of FRP Rods by Pullout Testing
Annex J
Test Method for Creep of FRP Rods
Annex K
Test Method for Long-Term Relaxation of FRP Rods
Annex L
Test Method for Tensile Fatigue of FRP Rods
Annex M
Test Method for Coefficient of Thermal Expansion of FRP Rods
Annex N
Test Method for Shear Properties of FRP Rods
Annex O
Test Methods for Alkali Resistance of FRP Rods
Annex P
Test Methods for Bond Strength of FRP Sheet Bonded to Concrete
Annex Q
Test Method for Overlap Splice in Tension
154
SG.01 (24) DESIGN AND SELECTION GUIDELINES FOR FRP PULTRUDED STRUCTURES
JSCE (Japan Society of Civil Engineers)
JSCE TEST METHODS
Standard name
Title
JSCE-E-131
Quality Specification for Continuous Fiber Reinforcing Materials
JSCE-E 531
Test Method for Tensile Properties of Continuous Fiber Reinforcing Materials
JSCE-E 532
Test Method for Flexural Tensile Properties of Continuous Fiber Reinforcing Materials
JSCE-E 533
Test Method for Creep of Continuous Fiber Reinforcing Materials
JSCE-E 534
Test Method for Long-Term Relaxation of Continuous Fiber Reinforcing Materials
JSCE-E 535
Test Method for Tensile Fatigue of Continuous Fiber Reinforcing Materials
JSCE-E 536
Test Method for Coefficient of Thermal Expansion of Continuous Fiber Reinforcing Materials by Thermo Mechanical Analysis
JSCE-E 537
Test Method for Performance of Anchors and Couplers in Prestressed Concrete Using Continuous Fiber Reinforcing Materials
JSCE-E 538
Test Method for Alkali Resistance of Continuous Fiber Reinforcing Materials
JSCE-E 539
Test Method for Bond Strength of Continuous Fiber Reinforcing Materials by Pull-out Testing
JSCE-E 540
Test Method for Shear Properties of Continuous Fiber Reinforcing Materials by Double Plane Shear JSCE-E 541
Test Method for Tensile Properties of Continuous Fiber Sheets
JSCE-E 542
Test Method for Overlap Splice Strength of Continuous Fiber Sheets
JSCE-E 543
Test Method for Bond Properties of Continuous Fiber Sheets to Concrete
JSCE-E 544
Test Method for Bond Strength of Continuous Fiber Sheets to Steel Plate
JSCE-E 545
Test Method for Direct Pull-off Strength of Continuous Fiber Sheets with Concrete
JSCE-E 546
Test Method for Tensile Fatigue of Continuous Fiber Sheets
JSCE-E 547
Test Method for Accelerated Artificial Exposure of Continuous Fiber Sheets
JSCE-E 548
Test Method for Freeze-Thaw Resistance of Continuous Fiber Sheets
JSCE-E 549
Test Method for Water, Acid and Alkali Resistance of Continuous Fiber Sheets
JSCE-E 531
Test Method for Tensile Properties of Continuous Fiber Reinforcing Materials
JSCE-E 532
Test Method for Flexural Tensile Properties of Continuous Fiber Reinforcing Materials
JSCE-E 533
Test Method for Creep of Continuous Fiber Reinforcing Materials
JSCE-E 534
Test Method for Long-Term Relaxation of Continuous Fiber Reinforcing Materials
JSCE-E 535
Test Method for Tensile Fatigue of Continuous Fiber Reinforcing Materials
JSCE-E 536
Test Method for Coefficient of Thermal Expansion of Continuous Fiber Reinforcing Materials by Thermo Mechanical Analysis
JSCE-E 537
Test Method for Performance of Anchors and Couplers in Prestressed Concrete Using Continuous Fiber Reinforcing Materials
JSCE-E 538
Test Method for Alkali Resistance of Continuous Fiber Reinforcing Materials
JSCE-E 539
Test Method for Bond Strength of Continuous Fiber Reinforcing Materials by Pull-out Testing
JSCE-E 540
Test Method for Shear Properties of Continuous Fiber Reinforcing Materials by Double Plane Shear ANNEX D: NM FRP PULTRUDED STANDARDS LIST155
14.2 Design Standards
DESIGN STANDARDS
Design guide name
Title
ASCE/SEI-74
Load and Resistance Factor Design (LRFD) for Pultruded Fiber Polymer (FRP) Structures
ASCE (2010)
Pre–Standard for Load and Resistance Factor Design of Pultruded Fiber Polymer Structures (American Composites
Manufacturer Association, November 2010) under review by ASCE;
ACMA
Industry Guidelines for Fabrication and Installation of Pultruded FRP Structures
CEN/TC prEN 19101
Design of fibre-polymer composite structures
Commentary to CEN/TC prEN
19101
Design of fibre-polymer composite structures
CEN/TC prEN 19102
Collection of worked examples
CUR 96
Fibre Reinforced Polymers in Civil Load Bearing Structures (Dutch Recommendation, 2003);
EUROCOMP
Structural Design of Polymer Composites (Design Code and Handbook, 1996);
BD90/05
Design of FRP Bridges and Highway Structures (The Highways Agency, Scottish Executive, Welsh Assembly Government, the Department for Regional Development Northern Ireland, May 2005);
CNR-DT 205/2007
Guide for the Design and Construction of Structures made of Pultruded FRP elements (Italian National Research
Council, October 2008);
DIN 13121
Structural Polymer Components for Building and Construction (August 2010);
BÜV
Tragende Kunststoffbauteile im Bauwesen [TKB] – Richtlinie für Entwurf, Bemessung und Konstruktion (in German,
2014).
DIBt
DIBt – Medienliste 40 für Behälter, Auffangvorrichtungen und Rohre aus Kunststoff, Berlin (In German, May 2005);
ASCE MOP-111
Reliability-Based Design Of Utility Pole Structures
ASCE MOP-66
Structural Plastics Selection Manual
ASCE MOP-102
Design Guide for FRP Composite Connections
ASCE MOP-104
2nd Edition - Recommended Practice for Fiber-Reinforced Polymer Products for Overhead Utility Line Structures
EUR 27666 EN
Prospect for New Guidance in the Design of FRP
38800 Country Club Drive
Farmington Hills, MI 48331 USA
+1.248.848.3700
www.concrete.org
View publication stats